this is my first time growing tomatoes from seed, i started them indoors in a home made potting mix made from vermiculite perlite and pine bark fines which has served me well so far with other transplants, and im doing this all indoors, under flourescent lights about 3 or 4 inches from the pots(plastic cups), the temperature is around the upper 60s and lower 70s, which i believe shouldnt be a problem, it does however remain that temperature day and night, which might be a problem but i dont think its the culprit, and ive been watering them with filtered tap water, which i dont believe is particularly high in any mineral, anyways, i planted the seeds about 3 to 4 weeks ago and they came up pretty quick(4-6 days) and for the first week, maybe less, they were doing good, but they started to slow down, the undersides of the leaves started turning purple, and the green leaves started fading. by now, most of them are still trying to put out their first real set of leaves, the leaves are very pale green, with quite a shade of yellow, and the undersides of them are dark dark purple, at first i hadnt fertilized them at all, because the pine bark is part composted and i figured it would have kept them going for a little while, but none the less i watered them with fish fertilizer, it was that thick brown stuff watered down 2 tbsp to a gallon and i didnt really drench them but i gave them a good sip, that was about week and a half ago, they still continued to decline, and i am aware that the fish stuff is mostly nitrogen, it has little of anything else, so today i sprinkled generous amounts of garden-tone which has fair amounts of everything, but not a whole lot of nitrogen, but im not going to wait and see if this works, i hope this is enough information for someone much more knowledgable that i to diagnose the problem