Is this freezer burn or something else??

Yes, it's freezer burn.. LIke stated above, it usually happens when they have been partially thawed, then refroze. It won't hurt your reptiles at all...
I sell them at a discounted rate when it happens to me, or just use them up myself...

Thanks everyone! I guess I'll go ahead and feed them to my snakes then. There's actually a new reptile shop opening soon and I was able to get in contact with the owner to get me some frozen rats. If all goes well then I can continue to do business with him instead. I wish there were more shows in my area..I really liked the rats from Layne Labs that I got before.

Well, if it helps, you cna't judge a shop by the fact that the pinks have freezer burn... If they open and close the same bag, they're gonna get freezer burn. I make mine in packs of 12/25/50, etc so it doesn't happen, but I'm sure once they start using them at home and resealing, they probably get a little freezer burn...
The rats and mice get it too, you just can't see it for the fur...