Most of those pics are of the cast aluminum piece behind the mesh in the operators station. Yep its oxidized. Is it something to worry about? not really IMHO. It wont cause any structural issues and it is hidden from view.
Kubota's paint is crappy in general. My tractor came with paint that is coming off in sheets! Mostly the problem is with any parts painted gray. Poor surface prep is the root cause IMHO. Kubota wont do anything about it. Mine was like that from new.
Look at your ROPS. How does it look? Any rust? Mine has it. The fore-aft links under the operators station for the loaders are all peeling. It doesnt affect operation in any way, but it is ugly. Some day when I get motivated Ill address it, likely have to remove and sand blast. Then paint. And not with Kubota paint, its pure OVERPRICED crap IMHO. I bought my last spray bomb and from now on will go with mixed automotive enamel paint.
Some pics of my Kubota. Bad factory paint is a bit of a systemic problem for them