How to get the last updated date of a post from a WP RSS feed?

I have a third party tool which extracts feed content from our WordPress site, via our RSS feed: http://ontariotravelblog.com/feed

The feed provides me with everything I need, except for the last updated date of the blog post; it does include the published date, however this is simply the date the blog was first published; edits / changes made to the blog after publication does not affect this date.

Now what's interesting is that the ATOM version of the feed (http://ontariotravelblog.com/feed/atom) does include both the published date and the updated date, for example:

<entry>  ...<title type="html"><![CDATA[8 Songs for Your Ontario Summer Road Trip Playlist]]></title><id>http://ontariotravelblog.com/?p=5621</id><updated>2016-06-09T16:40:46Z</updated><published>2016-05-10T16:25:35Z</published> ...</entry>

Which is great, except that the ATOM feed is missing some critical content (in particular, its missing a number of "media:" elements, such as media:thumbnail, etc.)

So after all this, my question: Is there a way to get the updated field which is included within the ATOM feed entry to appear on the main RSS feed? (perhaps via some config option?)