Need help rdwc auto

Hey y'all I have a 12 6.5 gallon bucket rdwc system with 25 gallon rez. I got 15 auto flower pineapple express and they are dying. I'm a total newbie but have been researching like crazy . I germinated with Rockwool and all of them sprouted and looked great three days ago. Then everything went bad . I used ph water to soak rockwool and I followed the technaflora recipe for success kit as far nutes are concerned. Idk if I burned them or gave too much light they are about a foot away from t5 fluorescents. I used half the recommended amount of mutes but immediately noticed yellow tips. Did I over water? What do I do only three out of 15 are surviving and I need to do something fast any help appreciated.
 

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