What bitsy said basically.
If they're going into shed they'll be a little less active and sometimes won't take food anymore. Don't worry too much corns can go several months without food and still be fine, not ideal because you end up worrying about them but still, not eating for 2 weeks isn't the end of the world.
How to you thaw the pinkies? If its in water then I'd advise putting them in a plastic bag first and submurging the bag. Some people say that their snake refuses the pinkie if its wet, others say they won't take it when the scent isn't as strong.
If you do get worried then you could try braining them, not the nicest thing in the world but what you do is jab a needle through the skull of the pinkie and mash it around a little, just wipe the brain goo off on the pinkie. Snakes are like zombies, they love brain.