My smallest discus, been in the community tank got about 4 months, has been hiding for the last couple of weeks.

sometimes just for a little while and then it comes out and swims around with the breeding pair, and often also with the yellow mellon.

I got home this morning and was adding some more plants/doing a water change, and I noticed that it was nestled into the corner, and not even responding to being touched.

I removed it to the breeding tank that I setup in the garage a few weeks ago, and he was just floating around, being carried on the current in the tank.

I added Discus buffer, and 1ml/7L of water of Big L Poultry wormer.

I don't know what the problem is, except that when he breathes something small and white comes out of his mouth, and then back in as he breathes.
intestinal lining or something?

any help would be great.

cheers.

elliot.