yea the helpful content update might have caused it.
Quote:
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If you host third-party content on your main site or in your subdomains, understand that such content may be included in site-wide signals we generate, such as the helpfulness of content. For this reason, if that content is largely independent of the main site's purpose or produced without close supervision or the involvement of the primary site, we recommend that it should be blocked from being indexed by Google.
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that seems new?
https://developers.google.com/search...content-update
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