Any Help with a ThemeForest Theme Not Being Responsive?

I've created a site for a client based on the CleanSpace responsive theme from ThemeForest. The site is pretty graphics-heavy and includes Layer Slider WP plugin.

The site looks fine from our side (15" and 17" macbook pro's). The client also has a macbook pro and the site looks fine. But she just had a group of investors look at her site and was angry that the slider and most all of the graphics are appearing HUGE in their browsers (Firefox, Safari, Chrome, most computers are about a year old).

Has anyone had this sort of problem or know what could be causing the site and slider not to resize?

Note: The site is behind a 'coming soon' page so I think I would have to coordinate with you to view it. Thanks for your feedback or help!!