Supposedly, this is due to excessive soil moisture during the cold season. Being a native to East Asia, they are used to cool/cold winters that are drier than in many areas of North America where they are grown. I had a bit of this last season but it did grow out of it and now looks fine,

Here in the Pacific Northwest Aucubas do best in dry shade. Our winters are notoriously wet, so dry, shady, places under evergreens makes sense here.
Mike