Healthy snakes can tilt their heads when they're relaxing, I don't think it means anything, & BPs aren't the fastest moving snakes either. Hard to say if what
you're seeing is significant or not...neurological issues can be caused from being over-heated or over-exposed to say, Provent-A-Mite (aka PAM), but we aren't
seeing your snakes to diagnose...sure hope it's only that you're over-thinking this & worrying needlessly. You said you just added a few snakes, but for how
long have you been keeping snakes before this? I ask because I've been keeping snakes for many years & often can tell that something is off even when a
vet sees nothing amiss; if you're real observant, you might be right that something is wrong with them, but no way I can tell you for sure...wish I could. This
isn't so much a symptom of having mites, but mites are thought to be disease vectors (-they can carry & spread diseases). Did all your new snakes come from
the same source? or different ones? Sure hope they are quarantined from your others & that you are practicing good isolation techniques? Are they eating?