Portrait view on phones no longer showing full-screen of main blog section

Hi, this site displays correctly on a phone when held in landscape position, but not in the normal portrait position. The site uses a 2012 child-theme (updated to 3.7).

I’m unsure of how this recent problem originated — it had been showing the main section with blog posts full screen in portrait mode, then with sidebar widgets following if scrolled down, which was fine.

Wondering if there is a quick fix to return the portrait view to a full screen of the main centered blog post section…or if possible just the full page including sidebar widgets.

Thank you!

The page I need help with: [log in to see the link]