Molting???

[Stacyskinrood]

I have 5 hermit crabs in my classroom. A student took them home over the summer, when she brought them back the entire tank floor was filled with sand for their floor. About 3-4 weeks ago I changed out their tank and put coconut fibers back in with a small sandy area. Within a few days all of the hermit crabs buried themselves (I can only find one now buried) and except one none have come out. Could the previous sand have been a problem for them and when I changed the tank they all buried themselves to molt? The tank does not smell funny but I am not sure if it would if they died when they are buried. I also do not want to harm them by digging them up. How long do I wait? It is just strange that they are all buried at once, hoping they didn't bury and die. Any advice?

[Wai]

Burying is normal; they have not been under for all that long and it is possible that they are moulting.

[Stacyskinrood]

Thank you!!