Red Blotches On Fish, Fish Not Swimming

hi please help about 3 weeks ago one of my algae eaters was not able to swim, he was struggling and could not swim up and he was on his side after about 6 hours he was much better and able to swim around the tank. last week he had a few red blotches on him that soon turned brown and dissapeared, this morning he had reb blotches all over his belly and top of him, he is not swimming but still breathing. please help!