Hi Nick,
Which section do you mean when talking about custom CSS? I think I haven’t installed anything specific to change the appearance for my website except for other genesis plugins/widgets. Here you can see all my installed plugins: https://i.imgur.com/VESM9rw.png
Weird that something is conflicting. I also saw that in the standard version you can select the image size for the featured image, is this also something that is normally visible?
I can give you my login information if you are really curious to finding out the problem. But then again I need a way to give that in private.
Thanks,
Sam