sick little clones..

alright guys. so without the long back story, my buddy gave me some clones to try and bring back to life but i've never dealt with clones before. they were worse off then this (sad i know) but started showin some signs of comin back after i got them in a controlled environment.. so they're just starting to root through their cubes and now they're going yellow and getting burned edges, also i've picked a couple dead underleafs if it matters. any ideas on how to bring these babies back to life?