You are lacking Ca+Mg. A result of small foliage and fruite could be from over N fertilzing but if there was no burt leaves then it is Ca problem. A CaMg my need to be added. When you go from soil you must replace all of the vits and minerials that where in the soil. Folvic/Humic Acids are needed along with Micro and Macro nutrients. Once you replace these elements, your plants will be strong and not have problems associated with using only synthetic fertilizer.

I use a basic 3-part, Ca+Mg, and a sea weed/compost mix for feeding leaves, that alone keeps the plants very healthy.

Hope this helps.

What? How the heck do you get CalMag deficiency from that post?

Your problem isn't CalMag. Maybe you do need CalMag, but nothing in your post suggested it. Your post did, however, suggest you have weak lighting that won't allow the fruits to get big. Your post here doesn't mention it, but I do recall you mentioning in a previous post that you use T5's.

I experimented with T5 lighting versus sunlight with cherry tomatoes. I also tried Brandywines (my absolute favorite tomato), but not as part of my experiment. I discovered without exception that the T5 lighting produced tomatoes that were significantly smaller than tomatoes grown in the sun using the same nutrients, water source, and system. Actually, I used 2 different nutrients. I had two cherry tomato plants inside, so I used Botanicare and GH on one of each. I did the same to each of the two outdoor plants. Difference in nutes didn't affect plant growth, but I did have to adjust pH more with GH. The plants in the sun also didn�t experience near as major of pH swings as the ones under T5 lighting in general. Outside, I had to do little pH adjustment. The tomato plants outside got twice as big, produced twice as many flowers (actually, it was over twice as many), had much denser vegetation, and the tomatoes were twice as big (3/4 of an inch compared to 1 1/2 inches). The indoor tomatoes didn't taste nearly as good. The plants were all from the same mother plant, so they were genetically identical, too.

Moral: Small fruit is often a direct result of poor lighting. You will get smaller tomatoes on a bush variety. A fast growing vine like Brandywines require even more light.

Clarification: When I say my tomato plants got twice as big, I meant in overall biomass, not height. The T5 lights led to plants growing taller. Again, a hallmark of poor lighting.

Yes, if that is the case then you need a hps light.

Hi again -
Isn't it fun learning the hard way!

But, I do have CalMag in my nutrient mix! And actually the foliage is quite dense on the tomatoes - I can't get my hand in there without snapping off something. My main problem is a lack of fruit. :)

I've been reading about light penetration. And you're right, I am using T5. I'm starting to get the idea that the T5's are good for short plants only.

Would you think a short determinate would do OK with a T5? Or should I stick to my lettuce and herbs?

You need 27k t-5's. I am sure you have "mid day" 55k bulbs. The 27k is close as you can get to an hps (19k). You need low k ratings red light to fruit and high k rating blue light for veg./structure.

Florescent light intensity rapidly drops off the farther away the bulb is from the foliage. I have seen where large tomato plants have been grown with fluorescent. However, using many, many, many twin bulb fixtures placed vertically (instead of horizontal), and closely spaced apart in order to get enough light intensity, as well as to evenly distribute the light around the plants foliage (top and bottom). For my money I would just start with HID in the first place if I were to grow tomato's inside (indeterminate or determinate), and use florescent for the small plants like lettuce. But using the same idea, like using 3-4, 100-150 watt HID lights placed around the plants (in different spots) in order to give better coverage around the plants. Basically about the same amount of wattage as one 400-600 watt bulb (more or less), but better overall plant coverage because of the multiple light spacing.