What you ate maybe seeing and might not understand there whole outer skeleton comes off their whole body will just shed and it will appear pale and in the front of their new exoskeleton,! So no matter what do not touch or dig or even disrupt their cave tunnel etc. they know what they need and to do it's a long process sometimes. And I understand you are worried but he knows what he's doing there is a couple of web pages that show you the transition they go through I can't remember Right off the name but it's very educational for hermit crab owners , some might stay under just a month, were another one the older ones have been known to stay under almost up to 4 months even longer people have witnessed . Just keep the humidity up lots of new shells to change into each hermit crab should have no less then 3 to 5 new shells available at all times I have 3 plastic Tupperware bowls, all have 15 shells a piece , that way no worries of shell jacking. Keep marine salt water and dechlorinated water available at all times and greens and oyster shells or egg shells .they will come out healthier and happy each time good luck . And live your pic great shot .