I just noticed these today on Coby, my young Oregon Red Spotted. She's about 3 or 4 months old and on a diet of pinky parts and earthworms.
Today I picked her up to find that part of her tail behind her anus was sunken in and it looked like she had feces lodged in her vent. I took her to a friend who knows a little more on snakes than I do. Coby was passing something foreign. My friend gently pulled it out. It was a piece of bark from her bedding (I use coconut bedding) she had swallowed during a recent feeding. She bled a little bit but the swelling went down a lot. It looks like her anus has been stretched out and there's still some feces thats being passed. During this ordeal, my friend examined her and told me that based on her tail (which appeared slightly deflated) and her scales (some of which were sticking up) she is calcium deficient and dehydrated. I gave her a warm bath and I'm gonna go buy some calcium powder for her.

If her health continues to deteriorate, my local vet will work on garters (this friend of mine recently took one of her's in). Any advice? I'm in a bit of a panic. I've separated her from my other garter (who's doing just fine)