Miniature page outside the editor?

For some reason my pages shrunk to only the left side. This only appears in the actual app or web page, not in the layout editor.

Here’s what it looks like in the editor:
image

and here’s what it looks like on the app/web page:

What could cause something like this?

It would helpful if you showed a screenshot of the entire screen.

Do you have a container set up with 1-1-1-1 columns?

Or custom CSS?