There are a bunch of things that can cause BPs to go off feed that wouldn't do the same for a Boa (used as an example since you have them). Poor husbandry, overfeeding, feeding too large of a prey item, stress, seasonal changes. I have some females who would never refuse, some that will at certain times of the year and some males that are just a pain for the whole winter. As long as they maintain weight, I wouldn't let bouts of non feeding deter you. Balls rock!