CSS is displaying different to admin users than non-WP logged in users

Hello,
When I am logged in to Wordpress and view the site, it looks perfect, both from the Upfront interface as well as when just logged in to Wordpress with the Wordpress menu across the top of the web page. But when I access the site with no Wordpress login from multiple browsers (IE, Chrome, and Firefox), the site CSS is drastically different. Here are two examples:
1. The header is not sticky and scrolls off the screen.
2. The gallery (pages accessed when clicking on one of the homepage images (business, men, women, actor/actress &musicians) are displaying in a single column as opposed to the standard grid.

Can you point me in the direction for what might be causing this?

Monica