No need to change css. White space under yellow banner is not showing cause of columns, it’s showing cause wp adds p (paragraph) around the image. You need to remove it. Go that page, and in editor click on text (next to visual, top right corner), and you’ll see something like this:
<p><img width="2560" height="110" alt="long-banner1" src="https://www.familyhealth360.com/wp-content/uploads/2015/09/long-banner1.jpg" class="alignnone size-full wp-image-336"></p>
And it needs to be like this:
<img width="2560" height="110" alt="long-banner1" src="https://www.familyhealth360.com/wp-content/uploads/2015/09/long-banner1.jpg" class="alignnone size-full wp-image-336">
The same problem is on the second page. Just remove paragraphs and it will work.
Regards,
Sinisa