That happend to me too but in my case it was small pots, after transplanting i trimed the edges and everything was ok. But im a new grower and maybe in your case is something else in question, could be overnuting/watering but Im sure you'll find your answer, there are alot of good and smart people willing to help around here, just put more info.

By the way your plant looks nice.
Good job

Cheers