Me and my Girlfriend got us 4 hermit crabs two weeks ago. 2x violascens (where one died already

The alive violascens is pretty active at night, so is the clypteatus. We're a bit worried about our brevimanus, since he's burried since day 2.
We heard some noises for the first week, now he's pretty silent. We assumed he's probably molting but we did some research and he didn't search for a new house before digging away. Now we're a bit worried he's maybe dead, still we don't want to dig him out in case he's not dead.
Any advices? Do they molt without searching for a new house?
Greetings