Hermit crab died - unsure why

[VClementine]

I got two hermit crabs from petsmart a few weeks ago. I had them in a 10 gallon tank, both salt and freshwater, their substrate is play sand and coconut fiber. They have a cholla log, a coconut hut, and I gave them a variety of new shells in their tank as well. They have a good sized heater that I've got on the side of the tank and a hygrometer that's been showing their tank on average around 78 degrees and 95% humidity. For food I have been giving them a few options of fruit like apples and coconut, hermit crab food and a cuttlefish bone. I've been changing out the food and water every day to keep it from molding. One of the two hermit crabs was bigger and has mostly been spending all of his time in the cholla log, but I did notice he changed shells the other day into one of the bigger ones I had in the tank. The one that just died was much smaller, and spent his first few days totally buried in the sand, but then also started spending a lot of time in the cholla log and the cocohut. These past few days the smaller crab was staying in his shell but laying in the sand right up against the heating pad. This morning I woke up and found him completely out of his shell like maybe he had been trying to switch into a new one, but he was dead, half hanging onto one of the water bowls. I'm really trying to figure out if he died because I'm doing something wrong, or if it was just maybe from stress since I've only had them a few weeks now. Any insight is appreciated, it's my first time having crabs since I was a child and I want to make sure the other one stays healthy!

[hermitsinnc]

Unfortunately, he probably succumbed to PPS (Post-Purchase Stress Syndrome). Petstore crabs have already been through a lot to get to the store, and by the time you got him, it was probably too late. It doesn't seem like you did anything drastically wrong that would have caused his death.