2) Sort of an unanswerable question, but I'll ask anyway.
I have 3 trays off 36 starts. the seeds in one tray sprouted way later than the others and the plants grow much slower.
Identical p[lainting time, seeds, watering, light, temperature, containers.

The only difference is the potting soil.
Yeah, not seed starting mix, I know. Kick me.

What in, or not in, the potting soil could make plants
start later and grow much slower?

Who and what is that picture supposed to represent?

I was hoping to get an approximate time and/or size
when I can stop worrying about the little fellers/fellerettes.

The 'good' soil ones are 3" and starting to sprout the 3rd/4th set of leaves.
The 'bad' soil ones are just starting to squeak out
their first true leaves.

I remained shocked and amazed at the difference in size. If you plant them in a medium with 0 nutrition they would still
out grow the little ones. I wonder what's in the evil soil thats slowing the little ones down.

About damp-off? Theoretically not until well established in the garden, Sorry. 2 types of damp-off, one affects young seedlings the other teenage/adult transplants. Key: good air circulation and above all avoid excessive watering. Too wet soil in a stagnant air environment is the primary cause of damp-off and 90% of us over-water seedlings 98% of the time. ;)

I wonder what's in the evil soil thats slowing the little ones down.

Greater soil compaction = less air for the rootlets = greater moisture retention = greater chance of root rot development = slower growth for both roots and top growth.

Like Sandy said, a light, airy mix that doesn't compact makes a big difference. ProMix BX is great, with or without the added fungicide (I don't use the fungicide) but other brands are also available.

Dave

Any possibility that the sickly tray was packed with year old potting soil while the healthy tray used new potting soil?

I made this mistake several years ago and had a terrible sprout. Now I just throw any leftover directly out onto the garden and let nature clean her up over the winter. Think about how the critters respond to a nice warm moist media, with a measured amount of nutrient in place,
and pretty well sealed away from sunlight and fresh air.

By the way that Pro Mix stuff sounds pretty good and I will see if I can find some.

I always use my left-over ProMix the next year to start seeds without any problems. Maybe that's because I close it up now and it freezes along with the winter weather.

Yep, it's possible. its 6 months old at least.
Mght have been left outside.

It was miracle grow and some other brand. I don't know which is which.

All the rest is fluff.

GGG

Larry

The stragglers continue to straggle. Severely.
Should I feed them?
If so what?
I have fish fertilizer. And worm pooh juice.
But IIRC you shouldn't fertilize starts.

I don't think I am over watering as the other starts
are quite happy with the same watering regimen.
Compaction is not an issue. It's quite fluffy.
Something evil is in that soil, or the lack of something good.

The wimpy ones still have no true leaves or are just squeaking them out.

An alternative is to rip the starts out of the soil and replant them into something else.

Please advise

(Some of these I don't have seeds for any more, so replanting is not an option)

I have to do something.

I'd carefully set them into tall containers, like OJ cartons or 2-liter soda bottles with tops removed, burying them with good soil up to the top growth. Those buried spindly stems will strengthen and send out roots.

And KEEP THE LIGHTS CLOSE TO YOUR SEEDLINGS!

Bets

I can tell you what I did but I'm not sure that's possible anymore: I dusted my trays with 5% Captan dust. I don't know if it can be bought anymore.

I believe Maneb or Mancozeb are both available today as is Daconil--all of these are fungacides. But what you are looking for is both soil and folliage activity and I'm not sure which will work down in the root zone. There is another bio type fungacide called Actinovate which I use both as a soil drench when planting and then later as a
folliage spray. It works very well. You can find the Actinovate by Googling. Another thing you might try-and this certainly can't hurt you even if it doesn't work and you then go on to try any of the above-is to mix up a teaspoon of baking soda (sodium bicarbonate) in a quart of
water and water the tray with it. Spray it on the folliage also with a hand pump sprayer. Actually a pretty good home style remedy! You could do a couple treatments with this.

You need to check with your ag agent to insure Maneb, Mancozeb, Daconil, and Actinovate are all approved in your state for tomatoes (they are here in Pennsylvania and Ohio),
and the agent may be able to offer some other suggestions.

Larry

PRO-MIX 'BX' with BIOFUNGICIDE is a "General Purpose" peat-based professional growing medium, designed for the cultivation of horticultural plants. This formulation is lightweight, uniform and provides necessary conditions to establish plant growth. This high-quality product is suitable for a wide variety of plants. Enriched with Subtilex®, a high-performance biofungicide that prevents root diseases caused by pathogens, such as Pythium, Fusarium and Rhizoctonia.
Prevents damping-off and controls root pathogens such as Fusarium, Pythium and Rhizoctonia
Patented bacterial strain of Bacillus subtilis*- MBI600
Better performance and shelf-life over fungal inoculants
Improved germination and survivability of transplants
Enhanced plant vigor and reduced incidence of disease
Compatible with a wide range of chemical pesticides
Reduced management costs for disease control

*SUBTILEX is a registered trademark of/and the strain of Bacillus subtilis is a product of Becker Underwood, Inc.

you were right more or less.
The soil was light and fluffy on top. Seemed dry even.
1 inch down it was a soggy compact mess.

The plants are much happier in their new, fluffier home.