There are hundreds of webmasters complaining and worried that their structured data is messed up, because Google Webmaster Tools seems to have a bug where the reports show a massive decline in the number of structured data elements a site had compared to the previous day.
If you go to Google Webmaster Tools and view your structured data report, you and I both will see this massive drop. Here is a screen shot from this site:
Like I always say with Google Webmaster Reports, they are delayed, often run into bugs and issues and will be cleared up probably soon. So do not worry, you are not the only one seeing this massive drop.
Update: Google's John Mueller said Google is investigating.
Update: This was fixed today.