Try wiping them off with white vinegar.

Tried white vinegar and the residue didn't budge. Thanks though, I appreciate the help.

Over at the Kitchen Aid website, in the forum they have recomended Bar Keepers Friend to clean the beaters up. It happens. My sons have put them in the dishwasher, and BKP works great.
The forum is under customer service, a really nice place.

There's stuff called Cape Cod polish...they have cloths that will clean them and return the shine. I received these when I got some Arthur Court pieces that accidentally went in the dishwasher. Returned them to good as new.

Here is a link that might be useful: Cape Cod Polish

I always wash mine in the dishwasher, my KA is over 30 years old, and the beaters look as shiney as the day I bought it.

Possibly it's a chemical problem with your water? Do you have very hard water?

They have lost their shine, no big deal. Don't bother with polishes, they won't help it and they may not be food safe. That is just the way the new beaters are. You aren't suppose to dishwash them. It doesn't hurt them, just removes their shine.
I always dishwash mine. Could care less if the beater shines.