Is it just that one male yellow lab that's picking on it? Maybe it's a female and that's why.
It doesn't have sunken belly. It has black blotches on its underside that I couldn't see in the other picture. Face/ gills all look normal so it has to be aggression. Its normally just one
I think so... but uhhh... now its like almost dieing.... the only tank he can go in has some high levels... some ammonia and a bit high trates... but him in anway??