Default Template Missing Background Color–Site Looks Broken

Logged on to our website today and realized that the template most of our pages are using isn’t rendering properly. Most pages use the “default template,” and as you can see (https://fairsentencingofyouth.org/about/who-we-are) rather than showing a mobile-friendly white columned background, most pages are showing a black background under the gray text.

As a WP newbie, I shuffled through the backend looking for answers, and finally turned to the FTP to look at and edit the default template, header, and footer. However, I’m not sure what I’m looking for, and since no one has touched the files in the FTP, I think it’s unlikely to be a file problem, and more likely to be a settings or updating problem.

One more piece of context: we have needed to update the WP edition, WPZoom framework, and the theme for about a year now, which has caused a plugin to break. I’m not sure whether this lack of updating could cause issues like this one.

Thank you all so much for your help and please let me know what other information I can provide!!

Nicole