Well, when I got up Sunday morning and did a head count in the tank I spotted a “double” for Calypso on top of the sponge rock. Cortez had abandoned the lovely shell he came in for one of the spares. In this case I think it was formerly worn by “Dee” the departed snail. Later in the day he got apparently stuck in a perfectly vertical position in one of the deep crevices of the rock and couldn’t reach to pull himself out. This actually isn’t too uncommon when a hermit crab is either new to the tank (and therefore unfamiliar with the terrain) or has just changed shells and hasn’t adjusted to the new size and fit. I’ve had to bail out both Cali and Calypso not long after I got each of them.
Not wanting to further disorient him, I set him back horizontally on the rock—which Cali was then climbing on and upon touching down he proceeded to immediately back straight into her! She didn’t seem to mind the collision, but it was pretty funny to watch.
Later in the day he appeared to be stuck again, but not so deeply and as he was still in contact with Cali from earlier, when she started to move off the rock he grabbed hold of her shell and let her pull him up out of the crevice and onto the top of the rock. It was just too cute! 
From there he made his way down and has had no further incidents with crevices.
I cleaned the glass and stirred up some debris in the tank for Elle to feed on, but it just looked like way too much bacteria and algae floating around so I went ahead and did a water change, a little less than 2 gallons. Elle is spending more and more time out, so everything seems to be going well for her still.
The hermit crabs are right now each on different rocks. Calypso on the palace rock, Cali on the sponge rock, and Cortez on the Tonga rock.
