I never seen this before but I put some superdrive on it and it start doing this a week later...just a cap full
I had that a number of times before and it doesnt look like nute burn or a deficiency to me. My nephews thinks it could be from rapid growth. But I dont think it is from using Superthrive.
looks mag dif. and maybe a Little over watered. next time if you use it try a foler feed and lights off when and if you do it
Superthive you are supposed to add only one drop per gallon. If you added a capful, that is probably why