That is very good service from your anodizer, let us know how things turn out.
My suggestion is the same as Caprirs', water staining from the aluminum being in contact with something while it was wet. The water marks can be unnoticeable until after anodizing. We have had this happen with individual parts dried on a plastic rack but most commonly it arises from parts being allowed to touch on the drying rack after washing. We have also had it on the unmachined surfaces of bar stock and a frequent cause is bringing cold metal into warm humid shop. Water condenses on and between the bars in a bundle and creates all manner of blotches.
An open mind is a virtue...so long as all the common sense has not leaked out.