1/2 acre pond in east Texas. Stocked a few years ago and everything fine until now....

3 weeks ago noticed a large fish kill, still finding real lethargic swimmers today. The skin is peeling off from the dorsal fin back, some the whole tail is covered. They also have a brown goo covering the areas.

Pond has a well that flows in a few hours a day through a fountain head for aeration. We feed twice a day floating food from tractor supply. No catfish are coming up anymore to eat. Minnows in the pond seem fine.

Can’t seem to get pictures to upload from my iPhone, any suggestions? Says file type is blocked