I have an account on hostmonster hosting 5 domains. There is one primary domain say abc.com and others are added as sub-domains (xy1.abc.com) with actual domain xy1.com pointing to sub-domain xy1.abc.com. I noticed recently that Google has cached both sub-domain and domain separately. I believe this will be treated as duplicate content and may be penalized as such. Is that correct? If yes, what is the remedy other than shifting web host?