White space above header

My question: I’ve chosen a fixed header image, removed the “site title” and “tag line”, removed the social media icons and search bar above header, but it still shows a thin white line (about 1/4 inch) above the image. I’ve also tired resetting the Top Header Margin to 0px, -10px, 30px, etc. but nothing seems to help. Any ideas? Thanks for any help you can give,