Hello,
First, I have some questions & unanswered needs-to-know which could help you figure this out:
- You mentioned that "it looks like the site was penalized by Google". Was your site issued a manual/link/partial penalty or is this based off of metrics? Was there a message via Search Console/WMT? In the previous paragraph you discuss building links but one shouldn't assume, even if it fails the smell test.
- Explain what type of structured data markup you were using for areas affected. Were you using review schema for areas where reviews/products aren't featured? Is there JSON-LD markup on your site AND does it reference the same content on page via HTML?
- What does your Structured Data Report section look like in GSC/WMT? Errors? Did you test in the Structured Data Testing Tool beforehand? What day did this happen? What did MozCast or SEO chatter via the web look like that day?
Here's an older article (2015) via Search Engine Land by Tony Edward covering structured data markup penalty recovery - Ask yourself the above questions (or respond), read the article, and also ask yourself:
- Were my intentions honest? Was my recipe markup for a recipe? Did I buy links via Fiverr? Is this drop in rankings and traffic even related to structured data markup or backlinks?
- If I was doing everything with the best of intentions, is this the work of a negative SEO campaign? What does your recent link profile look like?
Write back - let's figure this out!
Beau