Sorry to hear that Ben....really sucks.
I"ve also heard that too high temps. can cause this. A lot of people keep their gravid garters like other colubrids, but it seems they do better with slightly cooler temps. or at least a means of getting to a relatively cool spot in the tank. Best of luck with you T.s.pallidulus.....keep me posted on her progress, I'd be VERY interested in some babies since my Maritime search seems to have gone south. Do you have any pics of the mama to be?
Roy