Help Plants are turning Yellow!!! :(

Hey guys I really need help I do not know what I am doing wrong and sort of scared I have a 6 quart water base with 5 girls and was in vegetative stage for a month and it started to show signs of flowering and so I switched to 12/12 with CFLs and 1/3 cup of nutrients every 4-5 days. It was dark green and growing wonderfully 3 days ago and had put nutrients and I have been smashed at work, working 15 hour shifts and I just came to check on them today and saw that they were turning yellow and it's scaring me like crazy so if you CAN PLEASE PLEASE HELP ME OUT AND TELL ME WHAT AM I DOING WRONG OR WHAT I COULD DO TO SAVE THEM THAT WOULD SAVE MY LIFE AND THESE 5 GIRLS LIVES!!! Please help me out today hopefully I'll have some pictures posted right now as well and please just load me up with comments and advice. Thank you very much!

you really need a good ppm meter for hydro. it looks like you're not ferting enough. but 1/3 cup in 6 quarts of water is hard to understand. 900 ppm on a meter or so, would be better but until you get a meter you won't know what the ppm is.

Check your ph, it's could be causing a lock out.

Has the level of solution lowered any as in , are they eating?

If you can't check it then

change your resovoir water and give a fresh feeding.

I would think a res that small you would hAve to change it or at least top it off every 3-5 days.