Cannot discover offer of mystery border, and therefore can’t resolve on it

I believe dumb asking this, nonetheless it’s already taken too powerful time and I will’t figure it out.

On a area I’m building, I’m getting a easy dusky border exhibiting up between the header and the body. I’ve checked out every imaginable ingredient in each the body and the header that can per chance maintain anything to rupture with a dusky horizontal line between the two and I will’t discover anything.

Nothing is decided to maintain a border, it’s now not a divider, and a lot others.

This is riding me nuts. Any thoughts? Thanks!