if you have White Labels on your domains - did you make a link to it “no follow” after recent google update? I’ve noticed large decrease (-400 a day) in visits from google since I launched webcams.gayescortclub.com which is White Label for Video Secrets. The decrease could have nothing to do with White Label, just coincidence, however it doesn’t change the fact that it’s all duplicate content.
I’m also wondering what’s google approach to subdomains - will the main page be penalised if subdomain has duplicate content? I guess yes.
I can’t see your main site getting a penalty for linking to a site with duplicate content. But yes, I do use nofollow on my white label links. Sensible thing to do as it’s just another sponsor / advertising link really.
Sub-domains are supposed to be treated as their own sites, which should mean that it would not penalize the rest of your site. Do remember that lots of people use these white labels on sub-domains without any problems.
Google SERPs are still changing quite a lot on a daily basis, your loss in traffic might be entirely unrelated to your white label and just due to the general flux in the index. Also remember that any changes, negative or positive, that you do to your site won’t necessarily affect your traffic straight away. There is always going to be a delay between cause and effect on Google. You could change something on your site and not see effect on Google until a month later.
LOL I know about canonical links. You need control of the site with duplicate content to use canonical tags. By definition you don’t have that control with a white label site unless you’re the sponsor - which is not the case with the people on this thread.