bagaii cardinal looking "sad"

[Milad]

i dont know whats going on, but one of my bagaii cardinals (i think the male) is looking sad, hes hanging at the bottom of the tank, eats some mysis but not alot. isnt swimming around much and looks a little brown compared to his bright white female friend.

ideas? what should i be looking for? i thought he was about to tip over a few times. hes not breathing hard, hes breathing really slow. he also hasnt been hanging out with his sexy wife, they are usually together.

here is what he looks like: