I bought a socolofi a couple days ago, and since I've had it, it has been laying on the bottom or wedging itself under a flowerpot. I can't see anything else wrong with it, except some nipped fins from my other fish. I've noticed its color is a lot darker. In the store, it wasn't acting this way. I've done some extra water changes to be on the safe side, but my others -- some kribs, another socolofi, a crabro, and a pleco -- are fine. I've seen it chase away the kribs a couple times, but other than that, it doesn't move. It's a 55 gallon, and there are plenty of caves and hiding places. Could it be just stressed? Should I do anything?