Originally posted by aslyfox could be but I don't think likely
dust removal set automatically every time I turn the camera on or off
more likely any problem is due to the fact I was photographing through the windshield of a moving SUV
I’m often surprised by the amount of “sticky” dust that can accumulate on a sensor, even with the dust removal setting. It usually shows up on cloudless sky shots, especially those that require some PP work, like your low-contrast shot here. Try shooting a few clear sky or blank wall shots (not through your windshield). You may find you need to clean your sensor, as I did after I prepared my last posting.