I would avoid that pet store like the plague...literally! A whole litter of baby boas sick and dying? Screams of IBD.
I'm terribly sorry for your loss. Were I in your shoes, I would wash my hands (quite literally as well!) of the whole mess and move on. I'd throw away anything that baby boa came into contact with and carefully isolate any other boas or pythons your might have and watch them very carefully.
If you want a boa, please, please buy one from a reputable breeder. I'd never buy a boa from a pet store or some random person.