I actually found that I have what appears to be a third page template for some BuddyPress pages I created today : http://distanceparent.org/community/members. That page didn’t exist prior to today. In the page settings, it’s set to the default template with nothing selected below the post in the way of sidebars. It’s settings are identical to this page, which I also created today, which displays 2 sidebars : http://distanceparent.org/testing/
Why are they different from one another – and/or where are the page templates being managed for this theme?