If you're worried about your mouse supply, take in a mouse or fecal samples of the mice and a fecal sample of the snakes to a vet and have a fecal analysis run to determine if anything is abnormal in the first place.
Are you allergic to vets or something? You seem rather reluctant to seek the advice of a qualified person who know what they're doing and knows how to help. If I had snakes dropping like flies after eating mice I thought to be bad I'd be in the vet's office the next business day to see what could be the problem.
Live mice can carry a whole host of parasites I'm sure...worms, bad bacteria, etc. So I think you need to determine EXACTLY what the cause is before you take the shotgun approach and give the mice any medicine you think might help.
For all you know it may be something wrong with the snakes, crypto comes to mind. Especially the not-eating and bloated appearance. Crypto is a pretty serious thing and to date no known cures are available. Whether crypto can be transferred via rodents, I don't know. If they're in close proximity to reptiles in a crowded environment, then I'd say anything is possible.
With f/t the chances are a lot less likely of mice being infected with something that can kill snakes. Freezing for 2 weeks or more is known to kill most internal parasites within the gut of rodents or other feeder animals. So I'd say switch your remaining snakes to f/t until you determine whats going on.
Are these your own feeders that you raise or are you buying live feeder mice from a pet shop? If its the latter, I'd consider a different source or inquiring if they've had problems with their stock making their reptiles sick. I personally don't think I'd ever feed my snake live feeders from a petshop. They keep them in less than adequate conditions and you never know what they're being fed or medicated with, or even what chemicals or diseases are running around the stores' animals. I raise my own and am confident they're healthy and well taken care of.
So until I try to help further, please PLEASE take your snakes or mice to the vet to see what could be the issue. I don't want to try to help and end up making situations worse than they already are.