How do I get rid of this white border along my background photos?

When I want to add another background to a section below another, this white line appears, but I want it to be seamless. Any ideas? 

Please post the URL for a page on your site where we can see your issue.

A link to the backend of the your site won’t work for us, i.e. a url that contains /config/.

Please set up a site-wide password, if your site is not public and you've not already done so.

Post the password here.

Adding a site-wide password does not allow anyone to alter your site. It only allows those with the password to see your site.

Please read the site-wide password and how to share a link documentation to understand how they work.

We can then take a look at your issue.

You may find How to post a forum question post useful.