Why are my mice prolapsing?

I thought I should update on this.

On Thanksgiving Day, I had 3 more mice prolapse. I was about to go crazy. But then I found a mouse who had diarrhea. That normally wouldn't be good, but at least it confirmed that this was probably being caused by an intestinal bacterial infection, as opposed to pinworms.

So I did a ton more searching on the internet, and finally decided on attempting to treat them myself. Taking one to a vet wasn't working out, since apparently mice only prolapse on weekends and holidays. I bought tetracycline powder packets that are marketed for use in fish tanks, 250 mg per packet. This was really convenient since the appropriate dosage according to the Merck link above, is 500 mg/L. So I put it in the water bottles of the grow up cages (the only places where I'd seen any signs of the illness). I also covered the water bottles in duct tape, to keep out light, since tetracycline is photosensitive.

The one mouse with diarrhea has recovered and I have not seen any signs of diarrhea or prolapsing in the nearly 3 weeks since. Yay!

I do have a theory as to why I was not seeing diarrhea on more of the mice. What I read indicates that suckling and recently weaned pups are the most susceptible to this illness. Also, rectal prolapses usually don't occur until after the bacterial infection is past (the mucosa in the bowel stay swollen for up to 45 days). So my guess is that the baby mice were infected while quite young, and since I try to leave colonies with newborns alone as much as possible, I would never have noticed any diarrhea.

This does mean that the infection may be in my entire colony, and since I only treated the grow up cages it may reoccur. If so, I'll treat the entire colony, but I avoided that the first time around due to any possible problems with medicine would cause with pregnant or nursing moms.

I do wonder if mice treated with tetracycline are safe to feed to snakes? I am waiting for a while after I stopped treatment just to be sure.