I've had my Bolivian Ram in my established community tank for the past 4 months, and (s)he's been totally healthy until now. He disappeared for a couple of days and has now shown up but is just kind of sitting or crawling along the bottom of the tank. He's dark whereas before he was bright and shimmery. All his tankmates seem completely fine and all the levels are good.. What could this be? He isn't eating and won't come out from hiding, even when I put bloodworms in.

I recently got a new bulb, could that be why? He has plenty of plant cover so I wouldn't think that that was an issue.