Bead Blasting can cause that to the Finish, and also the anodizing process, Bead Blasting is a bad idea, unless you have clean uncontaminated Beads, just for doing aluminum, and you get a perfect uniform finish, which is hard to do, water bead blasting is the best, as it takes away the oxides and leaves a clean surface
To fix it, it would have to be stripped, and try to reblast it, or have the anodizer etch it