My betta has white edges on some parts of his tail. Is this finrot? I have API Fungus Cure and Maracyn Plus. Both say they treat finrot. Should I use one? I currently have 7 harlequins in quarantine after discovering fungus (I think? They still have it despite treatment) on two of them. Maybe they got the betta sick? This is so frustrating, I don't know what to do to make everyone healthy. Any help would be greatly appreciated.