I don't think that 4 mice in one meal is too big of a meal for an adult BP. I do prefer to feed mine on a weekly feeding schedule, but I've heard plenty of people say they feed every 2 weeks that seem to have happy, healthy snakes, so I don't see the 2 week feeding schedule as detrimental. When I used to volunteer at a zoo, they only fed their BPs once a month.
I doubt the feeding schedule would have been related to the regurge anyway, since the regurge occurred after a fasting period anyway.
Parasites is a possibility, and I'd definitely agree with the recommendation to look in to it. It shouldn't cost much to have a fecal done.