red devil Help needed!

My Male red devil in my pair has been excessively swimming upside down and head to the bottom. He is done this so many times I think he may have a problem so can somebody help me with them? It also seems his mate (my female red devil) is swimming perfectly fine with absolutely NO issues so it seems he may have a balance problem maybe.
To ALL the red devil keepers and breeders and just knowledgable peeps I need your help!

This is not just a Red Devil issue, it happens in all fish.

It sounds like he has a swim bladder issue. If he is still eating, feed him some peas. De-skin them and drop them in. If he doesnt take to them, Google swim bladder disease and find out what meds may help the issue.

GL.

My mother started attempting to feed him peas because thats what she feeds the goldfish sometimes He didn't want them. I'll google I guess

thanks madness alot of the things I just read say to seperate the fish from any other fish can I do that with a bonded pair.

yeah that's not an issue.

I think ill just sell them because I dont have another tank I just bought them and he has alwaysbeen like that soi think I got ripped off!