Leaf symptoms

The brown edges on your leaves are a classic sign of potassium excess, and the light green, thin leaves suggest it's locking out other nutrients (Cal/Mag). Ease up on the potassium, give your soil a flush to clear out the excess, and then re-introduce a balanced nutrient mix. Make sure your pH is in the sweet spot too, so all those nutrients can get where they need to go. That beeing said, if this started at the bottom(can't make that out) it could point to the other way around a potassium deficiancy.