Weird driveway stain

Hey all. I was wondering if any of yall have seen this before? The driveway did not need a pre-treat so I went ahead surface cleaned the whole driveway and then I went back and used a rust remover chemical that we bough from northern tool to clean some really bad rust stains. I finished up by spraying a post-treatment on the driveway. So again, any idea what these gray splotches are or how to clean them? Thanks in advance

Looks to me like it’s just a few places that still have some of the finished concrete on it, that’s not worn off. wouldn’t worry about it.