That is physical damage, or there was a problem for a very SHORT period of time while that band of leaf was developing- like, it hit the light or something. It's fine now. But it won't be for long if you keep taking your pH down that low in that soil
Set your pH to 6.7 for feeding in peat based soil that has already been treated with acid for so long and keep on top of your magi-cal. Lose the superthrive on day 1 of flower.
stinkyattic Reviewed by stinkyattic on . Brow and yellow? I went out of town on friday and came back today to have yellow and brow marks on 2 leafs. It is only on 1 plant and also just 2 leafs on the same leaf set. I snapped a few pictures for help. Let me know if you need more info. Rating: 5