Has anyone ever seen damage like this on 50" MMM blades?

This set of blades came off a tractor I just bought. The pictures show both ends of them blades. The deck was in nice enough shape apart from very dull blades. I changed blades and when I spooled up the deck I got sparks and clangs. Instant shut down and noticed a deep dent on the side of deck. The old blades didn't hit it, but the new ones did.

Hmm.

I fixed the dent and then went to look at the old blades. That's when I noticed these wrinkles and cracks. I have maybe eight sets of blades on a shelf and four more sets on decks. None have this damage.

Has anyone ever seen this sort of thing?