I’m not sure, but my guess is that your pages have a markup and a part in your style.css and subpages don’t. Could you see if your theme has a pages.php and a sub_pages.php (or something similar)? Your pages.php has a subpage navigation:
<!-- this displays the subpages - if any - in that red menu-->
<div id="sub_page_menu">
<ul>
<li class="page_item"><a href="https://johnmorgan.ca/?page_id=77" title="Various Events">Various Events</a> </li>
<li class="page_item"><a href="https://johnmorgan.ca/?page_id=69" title="Infrastructure">Infrastructure</a> </li>
<li class="page_item"><a href="https://johnmorgan.ca/?page_id=67" title="Family">Family</a> </li>
<li class="page_item"><a href="https://johnmorgan.ca/?page_id=68" title="On the Trail">On the Trail</a> </li>
</ul>
</div>
A subpage doesn’t, it only gives:
<!-- this displays the subpages - if any - in that red menu-->
<div id="sub_page_menu">
</div>
Now that I look at the code, it can’t be the stylesheet (<div id="sub_page_menu">
refers to that part in the style.css), so I can only think of the sollution that you have something of a subpage.php which lacks the get_menu or whatever argument.
So, have a look at the page.php and see what calls for the menu and check if you also have a php file for the subpages and see if you miss something.