Super bloated angel, please help!

I woke up this morning to find one of my angels breathing heavily on the bottom of the tank, belly distended double its normal size. I have seen him swim weakly, but he gets exhausted in the currents and goes back to the tank bottom.

It reminds me of a goldfish with a swim bladder issue but I a really at a loss. All I know is that it's not dropsy since he's not pine coning.

Never mind, He's gone now. It's just too weird though, last night he was just fine, and he hadn't even lost his colors by the time he died.