Here is how I solve the problem (hopefully) If I am not sure what's going on then I automatically cut back on the nutes....after checking ph of course. I find this to have more of a safety net than adding nutes and burning them. If you add less nutes and it's a def....you'll see problem increase. If it's too much the plant will improve. I have had both problems in my hydro setup and learned the answer by using this method each time. Good luck guys.