Theme not formatting correctly

[drjwbaker]

I love the minimal theme and have used it for a few different purposes. Last month I noticed, however, that one of my sites https://critcatdigipres.github.io/ has stopped formatting correctly whilst others (e.g. https://cataloguelegacies.github.io/) are fine. I tried rolling back some recent edits to no avail, so I'm wondering if this is a common issue with a quick fix (brief comparison of the two sites isn't showing any obvious differences).

Thanks for your help!