CSS suddenly died

Hi, I have been working on this design for two weeks https://allentragroup.com/usa
This afternoon after refreshing a page having not really done any important changes, the screen renders as a block rather than being stretched. I tried history going far back and they are all the same. Its like nothing to do with my design. I rebooted just in case, no difference. Really crazy help!!!

Hi, I have spent hours debugging. If I copy paste the short code for the webpage into another new page in the same site, it renders with the same problem. I have a multi site installation. If I select another site and do the same, the page is absolutely fine. It therefore appears to be something about the original site that is wrong, especially since past backups have the same problem. That problem, which I can define better, is that none of the rows are stretching as specified, they all show as a 1200 or 1400px block. Additionally, i have a background image as a hero section which has negative top margin to push the image under the header section. This has been working for weeks. But now the row does not move up, instead the image inside the row moves up. Another row with background image also demonstrates clearly that the row is not stretching. Something with the theme and this site seems to be affecting the design. I tried removing custom CSS and JS in theme panel, makes no difference. Same with the backups, its got to be the theme or theme settings but i looked over all the obvious things. Hope you are able to find something and happy to give you access.

the cause of the issue is that when you select a background color in the theme panel general color settings, it causes the effect i have described. This appears to be a nasty bug which cost me about a day of time!