Edges of seedling leaves curling up on serrated edges

two of my seedings leaves are curling upward along the serrated edges. What could be causing this ? They're both in 2 gal pots in sunshine #4, my temp range has been 71 - 79, 40% RH I also have them sitting on a heating mat. Ive fed them only once with 1/4 strength Botanicare Pro Grow, R.O water with 1/2 strength cal mag plus. The light is a 8 bulb 4ft t5 3" from the plants

http://i122.photobucket.com/albums/o258/Foosmatrix/leafwithcurlededes.jpg
http://i122.photobucket.com/albums/o258/Foosmatrix/Leafwithculrededges-1.jpg

you're fertilizing them when they are tiny as hell, do not fertilize. give them straight water until they are a month old. and dont water them constantly, they use so little water at that stage, so little