Wscook07started grow question 4 years ago when I mix my nutrients my PPM is only 120, When topping off my res. the PPM is at 40 & Drops to under 20 before topping off again. I have already burnt my plants a week ago but is that enough Nutrients? I cut it from 2 ml/ltr to .5 ml/ltr because of the burn (Advanced Nutrients)