[Plugin: Mass Custom Fields Manager] Automatically creating custom posts for new posts

Hello.

I recently used this plugin to add custom fields to all posts categorized as “books”. I changed my strategy and made books into a custom post type w/ metaboxes. I then removed the custom fields from all posts using this plug-in. I then removed the plug-in since I no longer needed it.

However, when I create a new post (or edit an existing post and save), the custom fields used previously for posts categorized as “books” appear in all posts. What do I do to stop this from happening?

Thanks,
mike

https://www.ads-software.com/extend/plugins/mass-custom-fields-manager/