I have a 7" feather fin catfish. Its skin is being eaten away from his body. he is in a 210g tank with a colony of geos and a few sevs. I just recently had an issue with my tank and lost about 10 fish. I treated the tank with some anti fungal and anti bacterial meds. thats when the issue started with the cat. I removed it and put in to a seperate tank for about 3 weeks. on the 210g I have now done 2 15-20% water changes after the meds. all other fish are doing fine. I put the cat back in the 210g after he was all healed up. now a few days later he is getting these same sores or flesh eating issues. tank perameters are good. what might be the issue. Thanks in advance for the help.