featured image on post now appearing as header image on post

Hi, My site is StonecropSister.com. I downloaded the theme yesterday, and had no issues with defining 4 posts and their featured images for the slider. Today I added a new post. On the main page, the header has my header image, and my slider images are showing up ok, including the featured image of the newest post. but when I click into that post, it is now showing the featured image of that post as the header image. what am I doing wrong. I have looked at the other posts, and they look identical in the settings. thanks, Nancy