I planted 32 tomato plants, and all have been infected by some disease. They were started in 3.5X5" pots, I used sunshine Mix 4 growing media, which has mychorizal in it. 16 hours of artificial light per day. Temp of the growing area was between 70-80, and fairly humid. Peppers I had in the same area grew beautifully, already blossoming, as well as cucumbers, seed grown apples, a variety of herbs, plenty of light, no plants have been leggy. Plants started to thin out, leaf branches dying off, main stem developing a Tan/brown growth that appears to girdle them to death. Roots are still very nice and white, no brown or black rot. I only bottom water and used a dilute fertilizer when them started getting thin, which didn't help. All plants used same grow mix, however it's not sterile. Why are only my tomatoes sick? I want to prevent it next year.