Spots on mice??

[Bogertophis]

I agree, that looks like "freezer burn" to me also- it's what happens over time in a freezer from the drying effect of cold air & time. It's mostly a cosmetic issue, IMO- not really a safety or quality problem for snake food, meaning your snake won't care or get sick from it, but it's also not a "good thing" to see on newly-acquired frozen prey, & would make me buy elsewhere in the future. (It also happens with meat that we keep in our freezer for too long- it's lost a little quality but is safe for us to consume as usual- ie. cooked.)

The OP mentioned these feeders were "repackaged from..." which suggests they've just had more time & exposure than is optimal. It's best to avoid those selling "repackaged" prey- as it was discovered in the past when another large rodent supplier had done the same thing- and in order to repackage what they were re-selling, they had to THAW a giant block of rodents, some of which unfortunately thawed too much which allowed some spoilage- not discovered until ultimate recipients of the rodents tried to thaw & feed their snakes- as I recall some snakes got sick or refused to eat, & when thawed, it was obvious to their humans that the rodents had spoiled.

You never want to re-freeze thawed rodents- that is a "quality issue" as well as a food-safety one. You can often tell when rodents were refrozen because they tend to fall apart- also the belly may loose fur & look dark in color- in other words, they're spoiled. That's because these are whole animals, whose entire GI tract is loaded with bacteria that grow prolifically once the temperatures are optimal (ie. when they're thawed); re-freezing does NOT kill the spoilage produced while thawed.

So what I'm saying is, I'd be cautious in this case. While freezer burn won't hurt anything, the knowledge that these are from a source that repackaged them means they're more likely to have spoilage, & in the future I'd buy from another source that doesn't "re-package". These should be SAFE to use IF your nose (once they're thawed) doesn't smell spoilage, they don't appear to be spoiled (beyond the freezer burn spots, as described above) & your snake doesn't object: if your snake eats them they're probably fine, unless we're talking about a species or individual that's willing to eat carrion.