First thing off the top of my head. Where did you get this trio of young BP's - breeder or pet store? If from a breeder, have you contacted them for advice and information about previous successful feeding methods used? If from a pet store, you've likely got the "they are EXCELLENT feeders, yes they are" sales line. When you purchased them what information were you given about what they ate (rats or mice), size of prey and method of feeding (f/t, p/k or live)? Whatever feeding program you want to do, now is not the time in my opinion to deal with that. Go with whatever worked for each particular snake until they are eating consistently for you, then slowly you can try to switch them to whatever you prefer.

Just as an example, we have an 06 female BP I did buy from a petstore. We raise our own rats...she apparently hates rats LOL. So for now we try every other feeding to introduce a mouse scented rat pup. She at this point won't even look at it so it's replaced with her favored adult mouse (though quite honestly a white rat pup and a white adult mouse are darn near identical LOL but she knows the difference). At some point she may go over to rats but for now our focus with her is to make sure she eats even if we have to purchase or end up breeding mice. In the end though it won't matter as it's been proven over and over that rats or mice, as long as the snake eats enough of either it will grow and do just fine.

Last questions. Are you handling these three babies at all right now? Have you had fecals done to make sure they are free of internal parasites that might be affecting their feeding response? Have you double and triple checked your husbandry against our caresheet? Are they in a quiet part of your home where normal noise and movement isn't scaring and stressing them out?