Sick Bala Shark?

[Coldwater]

One of my biggest Bala sharks looks sick to me.It keeps its head down and quivers alot. The tail and fins look like they have been nipped at. The fin bites are probally from my parrot fish and ompak catfish (I dont think this is what is is called, it looks sort of like a glass catfish but is blue.).
Also the very back edge of its gills are pulled forward. Is this from poor water quality?

Matt