I'm an overwaterer from way back, but I would say that once a week may not be enough and, if the leaves are curling, the plant is under stress and probably needs more water. I would also fill up the pots with some more soil-less mix.

Linda

I'd put my money on fertilizer burn but that all depends on the brand used. Some hydro ferts, even at 1/2 strength, can be too strong for young plants. Alternatively, what is the canopy height of the LEDs? Ambient air temps around the plants from LEDs can get suprisingly high if too close. Just a guess based on the info provided.

We did some limited testing using LEDs in the greenhouse this past spring and honestly weren't impressed with the results when compared with fluorescent lights.

Dave

Giving nitrogen fertilizer to young tomatoes can cause problems, and it's usually unnecessary. Sometimes, it can help, if the soil is very deficient or imbalanced, but it's easy to burn tomatoes that way, even if they need it. Normally, the tips of the leaves would be burned first, but I guess what happened here is probably possible. Anyway, if you have to give them nitrogen, using urea from Greenway Biotech would probably be gentle, as plants don't use it as fast as some forms of nitrogen. I've found that it doesn't burn plants easily compared to say Miracle Gro 24-8-16 fertilizer (which burns really easily). I'm not sure what's in that stuff, but it's really easy to burn indoor tomatoes and such with it. Outdoor plants don't burn as easily, I've found (but that might be because of higher levels of potassium and calcium in our outdoor soil, as well as the sun).