Theme Update

I’m very new to WP. I’ve landed here to hopefully resolve a maddening issue on my own. My client’s site has somehow changed to include 3 columns in the “Lifestyle Child Theme of Genesis” all of the sudden, and we have no idea when, or why this happened. The 3 columns which include Primary and Secondary Sidebar widget are showing up on all the pages and now interfere with posts on the other pages.
I’m afraid I know extremely little about coding. So I copied a code I found here to the CSS section. Any and all advice very welcome.

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