Header & Main Container Margin On Single Post

Thank you for the continued support. Objective: Adjust the Bottom margin on Header and the Top Margin on Main Container {Including the Sidebar}.

I was able to create a Breadcrumb using GB that appears under the header. There is an existing global margin on the header and the container that creates an unsightly space between the breadcrumb bar that was just created.

Since the breadcrumbs will appear only on posts, I am trying to edit the margins only on single post pages. When I use ' .single-post #main ' to edit the body container, it adjusts only the post content and not the side bar.

I cannot seem to find the reference to edit the header margin on a single post. As always any help, would be greatly appreciated.

Since I've made a number of other CSS edits to the header and post container, I'd rather not utilize GBlocks - as I'd have to start from scratch ... and oh so close to being done with all of my desired modifications.

Thanks again for the great support everyone.

Image attached - the margin space is subtle, but its there.