Scoring one or two points higher on the AB section isn't really that weird - it happens fairly often from what I've heard. Not to be mean, but chances are you just didn't do as well on the BC portion of the test. Usually rescores are only if something really, really weird happens (like you felt like you answered almost all the questions on the test correctly but you earned a 1 or 2). Unless you feel that you are absolutely, positively certain that you deserve a higher score, I wouldn't do it.
Don't feel bad, though. BC is a really tough test, plus you got a 4 on your AB section and that can count for college credit at almost all colleges.