Several days ago I noticed that my tortoise's shell was becoming softer and it was almost like there was an air bubble under the shell. He was still eating that night and seemed better yesterday, the shell returned to normal and he was active as usual. This morning when I went in to check on him his undershell was hard and his eyes were sunken in and there was a fowl smelling liquid secreting from under the back of his shell. I thought he was dead, but then he began moving, not far only about an inch or two, but then he rolled over onto his back. I had a tortoise die a few years ago and this is exactly how he was dead. What could be going on?