I agree with Keriann. Yes, you should really let them dry out. Matter of fact, once my seedlings are as big as yours, I let them dry out pretty much all the way before I water again. You can tell they need watered when you pick up the flat and it feels light as a feather. Then after you water, it's much heavier. Your method of bottom watering is quite unique, I must say. I think that most folks bottom water the way I do, which is to say setting the cells or cups into a tray of water and letting the plant absorb as much as it wants until you see moisture on the surface of the soil (usually takes anywhere from 5-20 min). Now, I can't say for sure what positive or negative effects your method of watering might have, except that it sure sounds like a pain in the hiney to me, and I somehow doubt that the soil is getting properly saturated. You want to simulate mother nature; a soaking rain. Then you want to let the soil dry out. That's how it is in nature. Roots need water yes, because the plant needs water, but then they need to dry out and get oxygen. Damp soil all the time = no oxygen to the roots. Now, I can't say for certain what part of your program is causing your issues, but I would start bottom watering them as described by letting them absorb water sitting in a tray. I think you will find that using this method, you should only have to water every 3-4 days, or less. I would lay off the ferts for a while, and then make sure only to fertilize when the soil is already damp, or you will burn the roots. I just mix the fert with water, then pour into a tray and bottom water as usual. Give this a shot, see if that doesn't help.

It's watered deeply about once a week. Osmocote was applied about three months ago. It has been developing new growth lately, which looks healthy and has a few lemons which have been green for a long time (more than a month?)

The image is quite small to be certain of anything. Can you please post a larger version? Also, as to the leaf bending, it would help us the most of you also post a picture of that. Thanks.

First of all, yellowing and brown spots on the leaves of tomato plants can be a sign of different types of diseases, such as early blight, late blight, or septoria leaf spot. These diseases are usually caused by fungi that thrive in warm, humid environments and can spread rapidly in crowded, humid conditions. Based on your description, your tomato plants may be experiencing some type of fungal disease. Brown spots on the leaves, along with the white residue you mentioned, are common signs of fungal infection. Additionally, the presence of fruit flies on plants could also indicate fungal growth, as fruit flies are attracted to the sweet odor produced by fungi. To address the problem, it is important to take some steps to prevent further spread of the disease. First, you should remove all infected leaves and dispose of them in the trash, rather than composting them. This will prevent the spores from spreading to other plants. You may also consider applying a fungicide spray to the remaining leaves, especially if you see new spots appearing. As for leaf yellowing, this could be due to a variety of factors, including nutrient deficiencies, overwatering, or pests. You mentioned that your soil was low in nitrogen and phosphate, so applying organic fertilizer was a good next step. However, it can take a while for the plants to recover, as the yellowing can be the result of previous stressors. As for fruit flies, you may want to try some natural remedies, such as using sticky traps or applying a dish soap and water solution to the floor. These methods can help reduce the number of flies without the use of harmful chemicals. Finally, since you mentioned that you are a novice tomato gardener, it's always a good idea to do some research and educate yourself on common problems tomato plants can face. I would recommend visiting a website like https://thegardenplants.com/pests-diseases/leaf-problems/, which from what I've seen has quite a bit of information on leaf problems on various types of plants, although I don't think there is an article on tomatoes many of the solutions for these problems are useful regardless of the plant in question. I hope this information is useful to you and good luck with your tomato plants!