Cory catfish not moving?

I have 1 male betta, 4 cory catfish, and 5 neon tetras in a 10 gallon tank. Today when I got home, I realized one of my cories is acting strangely. While the others are swimming all over the place like they normally do, one of the little guys was not moving or swimming at all. He seemed to be breathing normally, and when I put my hand inside the tank to move the ornament he was hiding behind (Not to intentionally scare him, I was trying to see if he had been injured somewhere), he quickly swam away and began scavenging around the bottom with the rest. Is this something I should be concerned with, or was he just perhaps sleeping?