What theme are you using? Have you tried asking in their specific support forums? (They might be able to assist with more familiarity with the set-up)
It’s a custom theme. I’ve figured out that it has to do with blog posts being configured within Custom Fields, but not sure what to add to have the custom field added as content to the feed entry.
This might be a good starting point: http://www.paulund.co.uk/add-custom-fields-to-rss-feed
You would want to customize it to the specific custom fields that you’re trying to pull and combine it with using the is_feed() conditional (https://codex.wordpress.org/Function_Reference/is_feed) in your functions.php file.
