Could have had a crab crawling over it. I know mine does all kinds of weird stuff at times. Changes in color, shape, extension. Haven't figured it out, kind of just let it do what it wants.
Yeah I will vouch that leathers do weird things. It looks like a healthy specimen. I had one once that looked like it was about to die and then all of a sudden overnight it just looked perfect and did very well. So they can just be weird sometimes. They are hard to kill in any event.