Notice the discolored white area on top of its head and the gill area. She looks bad.First, rule out ammonia.
Have you checked for flukes? I would rule out or confirm flukes via fwd next.
Have you seen any signs of velvet, brook or anything else? If not it may be best to get her out of CP and into nfg. It is possible to dose abx with cp. I use furan 2 if I have to run abx with cp.
Post a pic if you can get one.

