Ew. I'd be looking for a new place to get your feeders. Remember this is the ONLY source of nutrition your snake gets. Would you want to eat a diet that consisted only of wilted vegetables, meat products that came from animals already half-dead before they were slaughtered, etc?
In my experience, lethargic, not moving much mice or rats die soon. If none of your snakes will eat it, you might want to find another way to euthanize it.
Another possibility is to take it back to the store and demand your money back.