I have a russian tortoise, he is about 8 years old and I have had him over a year. He has grown a lot since I have had him! He is getting new shell, and has been since I got him. I lost him in my backyard this summer for about 6 weeks, and when I found him he had a lot of new, soft shell. It's been 9 months and it is still soft. Is that normal? When will it harden?