My tortoise, Bonnie, has a large divot or indentation on her shell in the center towards the back. She was a rescue and had it when she was a 5-pounder. It never changed as she grew and now at 85 lbs., it’s really obvious. Not sure how to post a pic.but have some good ones. Wonder if it’s an injury? Hasn’t seemed to have affected her growth although her scutes are really skewed now. Any theories?