Ah, you’re using Mantle which puts the images up against the container.
To remove this, add this CSS:
.separate-containers .post-image,
.separate-containers .inside-article .page-header-image-single,
.separate-containers .inside-article .page-header-image,
.separate-containers .inside-article .page-header-content-single,
.no-sidebar .inside-article .page-header-image-single,
.no-sidebar .inside-article .page-header-image,
article .inside-article .page-header-post-image {
margin: 40px 0 40px 0;
}
Adding CSS: https://generatepress.com/knowledgebase/adding-css/