I agree with
@KushGANG - I've got the same issue and all my research says that's what it is. I've started adding Epsom salts to my water/nutes for ALL my plants so no other will (hopefully) have the same problem. Nice thing about Epsom salts is that you can't give them TOO much... i.e., there's no amount that will actually damage the plant! Still, I've limited my addition to 3tsps in a gallon. I had rather expected to see a change in the "damaged" leaves but haven't - but since all the new growth is nice and green, I'm not going to worry about it!