Yoast SEO (also called WordPress SEO) is one of the biggest SEO plugins for WordPress and is used on millions of sites around the world.
If you're using ThirstyAffiliates in combination with WordPress SEO it's best practice to remove the ThirstyAffiliates affiliate links and link categories from your sitemaps.
This can be done by following this process:
1. Goto SEO->XML Sitemaps
2. Click on the Post Types tab
3. Ensure that Affiliate Links is checked
4. Click Save Changes
5. Click on the Taxonomies tab
6. Ensure that Link Categories is checked
7. Click Save Changes
Once you have saved the Yoast SEO settings, you should log back into your Google Webmaster Tools and resubmit your sitemap.