Custom CSS per template breaking responsiveness

I’m currently developing a site using themeforest’s “Avada” template.

My client required that different parts of the page are styled differently. This is working well by adding the following line into a copy of the “full-width” template just above get_header();

wp_enqueue_style( "all_modified", get_bloginfo('template_directory') . '/css/all_modified.css', false, "1.0", "all" );

where “all_modified.css” contains modified styling.

The problem is, when I do this, the site’s responsiveness doesn’t work. It scales correctly however columns will only scale and not drop down below one another. I have even tried calling an unmodified version of ‘all.css’ with the same code and this still happens. This only happens on pages where I’ve used this code.

A mock version of the site can be found at http://www.dutchmedia.com.au/newssa
The page with the custom css applied (currently a direct copy of the original css) is http://www.dutchmedia.com.au/newssa/entertainment/

Has anyone run into this before, or is anyone able to point me in the right direction to sorting this one. I’ve searched forums and have had no luck…

Thanks,