I Think My Fish Is Depressed

Is it possible for a fish to be depressed? Because I'm pretty sure one of my Bettas is having a hard time. Should I give him some of my anti-depressants? Would that help? What does he have to be sad about? He gets to live in The Pink Palace surrounded by all things pink, flamingo, and Hello Kitty. What could be better than that? I even have a buddy in his home to keep him company (they're separated by a plastic barrier, of course, but they can still chat and be friends). Perhaps they're having a lovers spat? Perhaps they're mad at me for keeping them apart? I don't know what to do. I hate seeing him so sad. I don't want to be a bad Mom. Any suggestions?