Yesterday this guy developed a small red blotch on his face which has now disappeared but as you can see it's spread, i have 7 other pleco's in the tank all of which are showing no similar signs. He's also the only one not trying to hide during the day.
Does anyone know what could be causing this or a possible treatment? His stomach is also swelled.

Does anyone know what could be causing this or a possible treatment? His stomach is also swelled.
