Sunday he had a bloated abdomen and frayed tail fin, but otherwise acted fine. Possibly he had a skirmish with a Coral Beauty whom he had been peaceful with 2+ years. Monday he continued swimming about though not with the "torpedo like streaking" 6 lines typically are known for. Also noticed his anus was bright red and he didnt eat. I planned to QT him today (if I could catch him) but he was reclusive and remained within the aquascape. Eventually he came out of the aquascape and layed on his side on the sand. I knew he was too far gone and suffering and I had to euthanize. After euthanization, I pressed on his abdomen and what seemed almost like a white tumor and pus came out. I couldnt see any worms with further autopsy so Im left wondering.......bacterial infection, parasite, stress induced bloat, tumor?