Cant tell very well by the pics. If it is a fungus, clean water and treat with a fungus med. It also looks like lymphosystus and there is no cure. I have been successful in getting it to go in remission and disappear. Daily 50% water changes, with water cold enough to drop the temp a few degrees each time.
He has it most noticeable there's one other that has a mild case but it looks like another one may be starting to get it which why I'm really alarmed i will start with the daily water changes! I read online that with lympho you turn the temp down everything else suggest turn it up so I think I should try turning it down a little bit since it didn't spring up on other fish until I jacked up the temp!? What you guys think? Side note it hasn't effected them eating or behavior they still seem fine I don't know if that narrows down what it has the potential to be
Lympho will not affect the fish until it starts taking over the body. I had great success doing 50% water changes daily for 10 days and each time I used cold water. The temp was always at 80* and dropped to 74* after every water change. Not a big deal. It was all gone in a week.