Son’s crabs buried, help!

[Hermiemom]

Without prior approval, my mother got my son three hermit crabs about two weeks ago now. I have them in a ten gallon tank in 6” substrate( a mix of play sand and coco fiber ) with two water dishes and leaves, driftwood, and a hut. I keep humidity high in the tank and temp is good from everything I’ve read. I had to do quick research and go out after she surprised us with them. Two out of three of the crabs are now buried and I’m worried they died but it doesn’t smell so I don’t want to dig them up. They have food and I change water daily. One of the now buried crab did change shells a few days before going missing in action. I’m stressing because my son loves Optimus primal and Leonardo and since having them I think they’re pretty cool too it would be a heartbreak I don’t think my little man can take. Is there any way I can figure out if they’re okay? Or anything I should do to help them when they come back up?
Honestly any advice would be helpful as I was not expecting to be a hermit crabs are parent and want to give them the best captive environment possible so they can enjoy their stay at my home

[Wai]

Hello! No need to be alarmed. Please read through the Crab Care section in the interim. Burying is normal behaviour.