Put in the oven during a clean cycle and scrubbed / oiled X 2 season.
The one on the left was fine 10 minutes later.
The extreme heat an oxygen made it rust after burning off all the crap seasoning. Scrub, oil, bake= awesome
I read up and putting them in the oven clean cycle can harm them by creating pits and damage, but it was way easier than scrubbing with steel wool for an hour