What is your medium mate? what is going on with your crop?? Seeing all those dead leaves and yellowing ones should be like a fire alarm: you are just about to loose control. My guess is, you are probably in Promix and most likely underfeeding. Please do yourself a favour, go in the question section. link some pics, and ask what is going on? give details like feedings stats, Ph with ppm of both intake and runoff, what is your medium. I am ready to help too. Good luck.