How do you measure the temps in the tank? What size tank? Is it near a window?
If everything seems right, no spikes in temp, no one sprayed any chemicals, she had water, then there's no telling what happened. Unfortunately, these living creatures sometimes just up and die without showing much of any sign at all. Reptiles don't show many symptoms if something IS wrong, so there may have been no warning.
Sorry for your loss. I hope your vet can come up with a definitive conclusion but don't be discouraged if he can't.
Hello
Thanks for your post the tank was not near a window and the temps are measured with a heat gun absolutely no chemicals and she has water always. I hope my vet can come up with something still cant get my head around it.