I've had 2 cory elegans for 6 months now - doing really well. Yesterday, 1 of them looked bloated, tonight he kept shooting to the surface, acting stressed, sitting on wood deco close to the surface. I put him in a breeding trap away from the other fish and now sadly, he's dead. Looking at the body I see nothing unusual apart from it being bloated ( the other elegans is slim ) & 1 of the gills seems red. Any ideas / help, please.