Catfish in garden pond
I have a garden pond that is 4000 gallons. I have koi and goldfish and native minnows and 2 brown bullheads that are 3 years old that I have had since they were fingerlings. One is 14" the other 13" long. Recently both catfish have developed red like sores or wounds on the back near base of tail. Did they do this on rocks? The koi are new as of 3 months ago would they do it? It's not ich. Is it fungal? None if the other fish show this. Looking for answers.