I got some 4 Julii cories a few days ago (among other fish) and today, since I got home a little bit ago, I noticed 2 of them are just sitting on the bottom in the same spot. One of them has moved a little bit, but he'll find a new spot and just sit there. The other one has been in the same spot at the back of the tank since I noticed. Should I be concerned about this? I've never owned cories before so I'm not familiar with their behavior. Water parameters are fine and the other 2 cories and other fish in the tank are acting fine. They were all active earlier when I fed them.