I agree, I think it's just something that happens. I'm sure there is an explanation but they seem to do fine. My snakes all eat the same rodents and I occasionally get clutches like that. They wrinkle up a bit but I've never had an issue. Good luck!
I actually have a pastel that laid 3 slugs and 2 eggs that look worse than that and both seem to be doing ok. Only at day 20 but so far so good. I have read that these "boob eggs" should be ok. Hatchlings may be a bit smaller but catch up. Fingers are crossed as these are my first eggs of the season.