After observing my Discus, Casper, I feel that he got burned by the heater after being chased by another aggressive Discus. He has a white swollen patch under his chin. Looks just like when we get burned and the skin turns white. Either he got burned, or got hurt somehow in the attack. He is staying up in a corner by himself and I know he just doesn't feel good. Any suggestions on what I can do for him? Any treatment meds that I can use on him, but would have to be put into the tank with the others and be safe to use?