Chemicals? temperatures? Lighting? Tank mates? tank size.... all of these could help us easier to help and pics too. Size? Also if he does not eat flakes or pellets try sinking pellets or bloodworms or brine shrimp.... sometimes they eat but u don't see them eat.
Could just be getting adjusted to the tank still. I just moved mine to a new tank and hes turned pink again and wont eat. :/ For being such a tough fish they sure are sensitive.
idk the chemicals, temp is 77, tank mate are other cats like id shark and pitus and
goldfish, tank size is 30 gallon grow out, size 3 inches, light nautral daylight