I talked to Phil Pelletteri this morning about your photos. There is definitely blister mite damage on the leaves, but the necrotic tissue is not likely due to the mites. Phil thought the necrotic tissue might be due to frost injury. It's possible that some of the necrosis is fungal in nature, but I'd need to see leaves in order tell for certain. The proof is in what might be sporulating in that necrotic tissue.
Hope this helps. Let me know if you have questions.