Hello @atoris
If I am not mistaken, that plugin adds the Schema data already
https://github.com/lesterchan/wp-postratings/blob/8d0ae923fa9f7cd809cd052a2a0dbf0e88b45011/wp-postratings.php#L1255-L1260
You should avoid adding the same Schema data again to your posts.
Please do check for errors in your post’s Schema data by using this tool
https://search.google.com/structured-data/testing-tool/u/0/
You can, however, use other Rich Snippets from Rank Math along with that plugin, like Article etc.
Hope that helps. If you have any further question(s), please let us know.
