Poor Hermit Crabs

Alright, WHAT is with our hermit crabs?  About a week ago, one left its shell, so we assumed it was sick and/or dieing.  We put it in isolation with food, water, and a couple of shells.  He moves around plenty (maybe even more than the healthy ones), eats and drinks.  If not for the fact that he's naked (which looks really weird, by the way), you'd think he was happy as a...well...hermit crab.  We still keep an eye on him, but have come to the assumption that captivity has just made him neurotic and suicidal (they were not pet store crabs). Then yesterday, we watched as another, much larger, crab climbed out of his shell!  WHAT is going on here?  We checked back in a couple of hours, and it was obviously dead.  Ryvre didn't want to flush it, so Dale took the kids outside and buried it under a tree.  Noone cried or anything, but Ryvre told me this morning "Mom, if i had one wish, i would want my crab to be alive again.  We could put a shell outside so he can find it"  *big sigh*