Some illnesses are airborne, which is why people recommend quarantining new animals in a WHOLE separate building then the established collection (different air supply). Since not everyone has the means to do so, housing the new ones in a separate room is your next best bet. There doesn't need to be direct contact for other animals to get sick (an example: mites. Mites can hitch a ride on your clothes from an infected animal and if you have one on you and you handle an established collection snake then that snake might contract them from your clothing. Doesn't need to be snake to snake physical contact).
What did the vet say about the bleeding? Did he say why they are bleeding?