Ok, I lied. They hide in their shell so well that I totall missed it. Both shells were next to each other as well the exoskeleton making me think a hostile takeover had occurred. That exoskeleton looks more like the hermit crab than I thought it would. To make sure I was right, I flipped over all the shells in the front of the tank and sure enough they all crawled away. So.... it was the exoskeleton, it's just more realistic than I thought it would be. Total noob post, lol.
I would definitely be down for a few shells, though. Thanks for all the help.