I treated this Kole tang and four other fish with copper about a month ago. I used carbon and a water change to clear copper. A few days ago his fins looked bad and some marks on his face and I thought maybe fin rot. Treated him for that and his fins are starting to look better but his head not so much. I did leave the carbon in for several weeks. They are in a 40 breeder for this quarantine. Water has been changed often and no ammonia is present.