Red Claw Crabs upside down, carapace/bottom opening and closing, then died?

Yesterday, I thought one died as he was sitting in the water on the bottom, but all of his legs weren't touching the rocks. He didn't run when I tapped him to see if he was alive. So I took him out of the tank and placed him in a container because it was late.. So then today I walk in the room and the other one was upside down. He was moving tho, so I knew he wasn't dead. So then I checked the one I put in the container, and there was a little bit of water placed in there too just in case he wasn't dead, and I could see him breathing or something. No movement in his body, but I definitely saw something moving by his mouth. So I thought thank god he's alive. But I didn't move him back to the tank bc if he was hurting, I didn't want to pick him up again. So as time goes by, the one in the container flipped upside down too. And the middle part of his carapace started to lift. I thought ok, so they must be molting! Well after about 40 min of it lifting and going back down, I saw, what I believe, was poo. Then the carapace closed up and now he's not moving even a little bit. The other guy in the tank was still moving though. His whole carapace started to open a lot more than the other one. And he looked like he was cleaning the inside or something or maybe pushing it off of him. As time went by, the bottom closed up and now he's not moving. I really think they're both dead now, and I have no idea what happened or how they died. I need help.