Is he surface moltng? I'm worried, please help!

[beepboop]

To reiterate, he's sitting still, has been in the same place for days, and has lost both claws and at least two legs. I suspect he is dead, but the tank does not smell fishy and I don't want to bury a live hermie. The other two have been buried in the same places for a week. I got them two weeks ago, and they seemed fine the first week and moved around the tank and all. I listed everything I do for them, and I would really like to know exactly what would cause this and, if they're not dead or for help if it happens again with future hermit crabs, how to "cure" or at least help them, how to tell if they are already dead, and, if it's hopeless, how long they will sit there in misery without dying.

[beepboop]

Thor died, and so did Captain Hammer. I guess I didn't notice the same thing going on with him, he was less visible.