Hi everyone.
I have a very healthy 8 year old 25 pound female tortoise. She has been acting funny for a week or two(wasn't very active, barely eating...) We took her to the vet, and they couldn't find anything wrong with her. A few days later she passed a huge stone. Literally the size of a golf ball! Her diet is fine, and the temperature is always in the mid 80's. I just can't think what could have caused this, and what can I do to prevent this in the future?

Thanks guys
Mike