What else is in that rack? Have you purchased any new animals? How old were these hatchlings?

You need to follow the strictest quarantine practices from anything in that rack from the rest of your collection until you figure out what is going on. I would do a total disinfectant scrub down of all tubs in that rack... and keep a very close eye on all the other snakes especially ones that were housed around them.

Not suggesting this is the case... A local reptile shop owner recently purchased a snake from a customer and brought it home to his collection. He didn't quarantine it. He started having minor problems with snakes not wanting to eat... Then he noticed what appeared to be slight respiratory infections in a couple snakes... So he bumped up the heat. Then out of nowhere snakes started dying. Starting from the snakes who's tubs surrounded the new snake then spreading out. The vet diagnosed the problem and he was able to medicate and save most of the snakes... But he lost a lot of snakes. I forgot what the prognosis was.

Not trying to freak you out or anything... Just worried about you. Quarantine big time and assume something contagious could be happening until proven otherwise.