Growing seedlings successfully is indeed a delicate thing - and sometimes even a quite controversially debated topic.

Some people get it straight away, and obviously see no problem with that part. All they have to do is repeat exactly the same thing next time. In fact, the key is to find a good technique and stick to it. Easy going in such case! But others who don't succeed with the first shot, struggle and get lost while reflecting about what they may have done wrong... and should do better next time.

The most frequent mistake people may make here, is to pick some technique here and some finesse there and mix it all up. That's not gonna work - what you need is a complete system, clear and unmistakable instructions (from a reliable source) and do exactly what they say... and leave your creativity and ideas out of the deal - just for one time. ;-)

The most reliable and sure way is to use professional seedling potting mix (mixed with some perlite), grow you seedlings as millions of gardeners do for ages, - and before repotting to your setup, clean the roots from the dirt (by gently shaking out the mix while dropping the roots in water). That's what will work for sure most of the time.

As soon as you use "inorganic" substrates or mixes and need to fertilize correctly, it's getting quite tricky. You said: 1/4 of strength. Here I need to ask: a quarter of what exactly? Well, because "30-10-10 powder, and 14-14-14" isn't really telling me much. I am using my own formula with 0.9 - 1.2 EC - from START but that won't help you much either, because you haven't got my formula. But in fact as low as 1/4 strength is suggested in general (some say 50%), because most people overdo it with fertilizing their seedlings. And suggesting 1/4 is simply avoiding this to happen. But In some/many cases 1/4 will not be enough. Seedlings that grow in amorphous and/or inorganic substrate need to be fertilized properly, to grow as they are supposed to. Here you should get a recommendation from a person who has repeatedly tested and successfully used product X with concentration Y in configuration Z. And certainly nothing in between, vague or unclear. Fertilization of seedlings is delicate and should be done by the book (what - or who's book it ever may be). Or, as mentioned before: you will be lucky or unlucky... they call it trial and EROR, don't they?

While a mix of perlite and coco peat is fine in my experience too, for Jalape (and other pepper seedlings) you may be better off with 75/25 Perlite/coco. Just because too much coco may retain too much humidity, something peppers and tomatillos as well, do not like at all. If you know how to properly water them, 50/50 may be fine, though...

Tomatillos are indeed very sensitive, can dump off for no apparent reason and in no time, even if already a few inches tall. They simply hate excessive moisture! Be sure to have at least 2 plants maturing and flowering, as Tomatillos are no self-fertilizers, they need at least one "mate" to be pollinated! (just a reminder, perhaps you knew that already).

I'd also recommend to grow more than half a dozen seedlings (of each) in the first place. Perhaps with two different techniques (media or mixes). It greatly enhances your chances of success. From 6 seeds there will most probably be 2 or 3 that that end up in not being as strong and nice as the winners. They'll be and stay latecomers. Best is to choose the strongest and nicest 4 from 10 before repotting to your setup.

Last but not least: as you have not been that lucky last time, simply do not try anything too fancy. It will not really enhance your chances of success but may be another source or reason for failure... ;-)

Best of Luck,
Lucas

PS: no strange time for seedlings for my understanding! At my place I do seedlings outdoors all year long. ;-)

Last summer I started numerous peppers in both potting soil and in a 60/40 perlite/vermiculite medium. I had plants both live and die in both media type, but by far the healthier plants came from the potting soil so I'd have to agree with Luc that soil is the simplest way to go.

When I have started seeds for hydroponics previously, I always germinated them on paper towels then transplanted them into a perlite/vermiculite mix and allowed that to sit in a shallow dish of water (a dish used for eating actually) until the roots came out of the net pots. I would then use a 1/4 strength nute solution for 1 - 2 weeks; basically until I got the pots into the system then one week more. After that I would switch to full strength solution.

I've never heard of covering seedlings with a dome other than seeing that done in pictures in catalogs. for rooting cuttings it is definitely required to maintain a high humidity, but for seedling, that shouldn't be too much of a problem. Not to say its right or wrong, I just have never done or seen it done.

In regards to the fan on the plants, my understanding is it is to strengthen the stems. I'm not sure it has to do with ethylene production though. Wouldn't the fans simply blow the gas away? brushing with you hands is probably overkill, but I don't think you'll hurt the plants. The most important thing to do to get healthy sturdy plants is to make sure they get enough light. Otherwise they'll end up getting all leggy in their search for it. you said you were using flouresents. Make sure you keep them as close to the plants as possible.

Covering with a dome comes with the benefit of higher (and constant) air humidity, which enhances germination and quicker growth. But also with the disadvantage and risk of high humitity issues, as development of fungi, dump off, etc.

The right aeration is a matter of experience and is linked to general conditions, temperatures, species etc. Some tray covers come with ventilation slots, which is a big plus. Those are supposed to aerate the mini-greenhouse and allow excess of humidity to evaporate.

And let me just add something about that 1/4 formula and explain why it actually is "not good enough":

If you cut any common nutrient formula by 4 (25%), you obviously cut all ingredients, as in macro- and micro elements by 4. While this might be OK for Nitrogen and Potassium content in some cases, - Phosphorus, Magnesium, Calcium, Sulfur and all micro nutrients simply (and almost always) come short with this equation.

In a very early growing stage of a seedling, it doesn't matter much because a tiny seeding is able to grow fine with very little (or limited) resources of nutrients. But it's nutritional needs grow exponentially. The longer you keep a seedling in such a "compromise-diet" the worse it is. Sooner or later they'll have signs of deficiency, or even worse: actually have some deficiency without visible signs.

And - this might be the reason why in some cases, seedlings grown in quality potting soil look (actually are) stronger, bigger and healthier as their brothers grown in 1/4 strength "of whatever" nutrient solution.

I could give a more elaborate version of the above" equation" for NUTRIENTS in numbers and data (together with an appropriate formula) if anyone is interested in knowing (or understanding) them. Perhaps only interesting for those who are able to put them in actual practice.

i would like to add a bit of my experience here if i could?

I ( not being too proud ) have had the most amazing learning curve of starting seeds. It was nothing more then two things, 1) nothing but time on my hands and 2) lack of patience requiring me to quickly figure out a good method. Granting what works for some may be ill advice to others as they have already adapted their own special way over their trials and errors, but here is a simple one I use..

I have been able to sprout catnip in 2 days.,

first, I like to get starter rockwool cubes, 1.5 inch cubes. i soak them in nothing but water then cut each cube to get 8 smaller cubes.

( I like to save money and with indoor growing, space is everything )

once soaked and cut, I place them all side by side in a shallow tupperware container, ( take out chinese containers big enough to fit one steak in size )

I place my seeds on a piece of paper, take a q-tip and cut one end flat. I dip the q-tip in water to wet the end, this will hold one seed to the bottom with no effort, then i push the seed into the middle of my cut rockwool, just twice the deepness of the seed ( give or take )

I thought for years that seeds need to be covered by soil, like they were vamps and would die if they saw sunlight, but that is not the case. the only reason why soil growers have instilled in us over the years to do so is two reasons, 1) to keep the seed as moist as possible and 2) to keep birds from finding them and eatting them.

Then when you place the lid on top, I cut too small holes. one in each end no bigger then a thin pen. this allows me to forget a day here and there ( like that would ever happen ) and prevents mold from building up.

WHICH is what i think is the big hype of lids. We use them to keep the medium moist, but prolonged under the right lights can cause mold which can kill off sprouts. as far as STARVing a plant of oxygen ? well, that is debatable, when a seedling sprouts, how much osygen is it really using in the very beginning of it's youth? now I am not talking months, but days.

But everyday we all should be popping that lid to at least say hello to our new friends to be........

Spending that time with your seeds, sprouts, seedlings and plants everyday is after allt he reason why we grow, is it not? talk to them, brush them, breathe on them, it's your zen afterall, and that attention could keep you on top of any issue that could accure....

Since i have two holes in that lid, their small enought o keep the humidity dome effect, but big enough to keep air inside, I do not remove the lid until i see the first seedlings sprout and rid themselves of their shell..

after that, I take the lid off, but keep it on, just add a little more air, even a pencil thickness gap.

then you will know when it is time to remove that lid all together, normally a few days after the first sprout I will remove the lid.

~~~~~~~~~~~OK~~~~~~~~~~~~~~~

now, once you remove the lid there are a few things I always keep in mind.

1) NOT ALL SEEDS will ever sprout and since growing indoors space is limited, thats ok, I only want the strongest of seeds anyhow. so the early spouters are the KEEPERS.

2) now that the lid is off, these cubes are going to dry out over time and attention daily is mandatory...... ( again, like we won't look at our seeds every day we wake up and get home from work right?)

Now comes the most important part of my zen, deciding when enough time is enough and those little seeds that still haven't sprouted must be pintched and tossed into the yard. they may grow one day, but their lack of speed is not valid in indoor gardens.

depending on how dry the air is or how hot the lights are at this point they will most likely need to be watered ( sometimes twice a day )

now that the cubes have been weeded out, strongest are growing, every morning and when i get home from work i take a turkey baster and the following,

schultz fertilizer 10-15-10 7 drop per quart

I put 3 drops in a quart, fill the turkey baster and drop this on each cube just till i see water coming from their bottoms,

twice a day, sometimes 3 times.

repeat
ZEN
repeat
No stress
Repeat
ZEN

once the seedlings grow for a week, I look for the healthiest, greenest, ( you know what your looking for )

once i see just a seeker root poke through the bottom of the rockwool cube,

I take them to their next home

( WHATEVER medium , style, method ) you are using.......

Sorry if that was winded,

It doesn't take too much for me to get into my ZEN with my passion to bring seeds to life, I can tend to get winded and a bit drwan out.

but if you got to this point and are still reading,,,

Aren't gardens just magic on earth?

i start all my seeds in 1.5x1.5" rockwool cubes.
just soak the cubes in water then put two seeds in each one and place the cubes on a plate and cover with the plastic cover from a cdr spindle. place under my 400w hps (between my existing plants). wet rockwool when needed.

thats it.