Help needed

[Glen]

Hello everone, I have a 160L tank with 3 blue torquoise in it that are about 5 years old. One of the fish is slowly losing condition. Its head is starting to taper, it is starting to develop a lump in the middle of its body and it swims (rests and feeds) with it head about 2-3 cm off the substrate. This has been developing over about 2 months now, however it is still feeding well and is still able to stand up for its self when feeding and interacting with other fish. I had 2 other fish develop the same symptoms and die (about 12 months apart). They were in seperate tanks with other fish (not the same fish as the latest case are with). Each time it was only one fish in the population that developed symptoms. The treatment I have used in the past was to treat in a hospital tank with epson salts @ 1 tablespoon/40L( I thought there could be an obstruction in the gut as the lump became visable before any noticable loss of condition), followed by a Metroidazole treatment @ 250mg/50L @ 33oC. No noticable change. Pictures attatched. Any idears appreciated. Glen.

[Annie]

Glen, I am sad to hear of the trouble you of had.
You said that the Discus us eating..do you see whitish and stringy feces. Maybe a parasite?

What about the lump, it could possibly be ulcerated.
could be some form something cancerous. in which I am sad to say, this from what I understand would be untreatable.

Any mucus or patches of anything present?