My leaves do this late in the cycle after Ive used Gravity. I dont really stress on it because the plant finishes wonderfully. I always looked at it like a chem burn. I add extra b vits and cal/mag for stress. Superthrive is basically a b-1. I prefer a b vit in the hydro world because Im in rookwool but there is certainly nothing wrong with the product. I dont think it will reverse the spots but slow/stop them. Hope this helps!