The fins look like little stubs and are white around the edges, i have a feeling it might just be from aggression because when i bought them from petsmart the guy said they had only gotten them in the day before, and they might just be to small for the tank right now, i have them in quarentine for now, i might just wait till they get bigger to return them to the big tank, my other mollies are doing just fine , it is just the 2 smaller ones that have the fin problem.