Lab Caeruleus blinded

[Hobbiest]

I had four Lab Caeruleus. One was picked on and had to be separated. The first time the chewed his anal fin down to nothing. I separated him for many months then tried him back in with the others. Within two days he had to be saved and I was done trying to put him back with them. The bad part now is although he is healed they seem to have blinded him somehow. No damage on the eyes but he is definitely blind. I am wanted how this could happen. Anyway, kind of crappy. And not sure what to do with him.