Betta Fish: Is my girlfriends betta “okay”

Hey everyone please be nice. My girlfriend doesn’t have the best set up for her tank but her fish has done decently well and we do water changes every two weeks to a month. All levels in the tank seem to be in order but she’s worried something may be wrong with her fish. The gray patch’s weren’t there when we had bought the fish about half a year ago from a petsmart and he has a new color stripe down his tail fin if that’s the correct word. I just want to know if this is normal and if not what I can do to help her.