Hmmm, could be frost damage, but it could also be Hosta Virus X. And I lean more towards the HVX. The American Hosta Society has information on Hosta Virus X if you are interested in looking. But above all, practice good sanitary practices and clean your tools between plants, so that if you do happen to have a hosta with HVX you won't unintentionally spread it to your other hosta.
