girls dying need help

this is my first grow i started with 3 purple haze seedlings.there 2 and a half weeks old.2 looked great while one not so good the 2 good loooking ones have died in the past 3 days the bad looking one is the only one left.the leaves are turning yellow from the edges what am i doing wrong im using a diy ebb/flow with gh flora nutes.6"mesh bottom pots w/hydroton
with rockwool cubes that the seeds sprouted in.i dont have a camera at the moment but should have one to use soon

Maybe you shouldnt have done any nutes so early.

thats what i was thinking.i was giving them a half strength but i was just experimenting.like i said this is my first real grow(unless you count those times in high school when i would just throw some seeds in some dirt in the backyard and just wished for the best)i have a couple bagseeds i started yesterday so im not to upset at least i know to hold of on nutes till later now

first time more is better thinking , sometimes less is more good luck ,step away from the young plant.............

thanks for the advice +rep