Yellow tomato leaves

Yellow tomato leaves

So, my seedlings are about a month or so along. I have my little guys under a flurescent light while they get strong and I am too lazy to get the containers ready, and they're developing a problem: the topmost leaves are yellowing and curling up from the sides. I'm certain it's a nutrient deficiency of some sort, and not a burn from the light. What makes tomato leaves turn yellow, and how do I fix it? If it helps, all of my varieties of tomatoes are doing it, including romas, super sweet 100s, some German and yellow heirlooms, and some pear tomatoes. They were stared in peat pellets, and later moved into small Jiffy pots. Thanks!
plant identification

plant identification

Yuck!!!

Yuck!!!

My Container Garden picture…

My Container Garden picture…

weird weather

weird weather

Floriade

Floriade

Newbie

Newbie