First I would assume that red mark is most likely an attack from the BP. Most parrots that I know of are suction feeders since their mouths don't close completely. As for the swollen stomach I would have to say its most likely either a female carrying eggs or it has possibly been over fed. But I am certain others will chime in with their own experiences and ideas on what it could possibly be. Hope this helps ya in some way.
I would suggest kanamycin or maracyn2 on top of the Epsom salt (1tbsp per 5g).
Odd location for an attack from the blood parrot. Not sure it’s coincidence if there’s bloat and redness. This is how septicemia for polys go. Just saying.
Yeah not sure. Not doubting ya, I just don't have much experience with polys. I only had the 1 ornate bichir and he never had any problems besides the clown knife almost eating him as a baby. But the red mark definitely reminds me the the marks my King Kong parrot used to leave on the jack dempsey. But from I looked up online your probably right.
