I'm trying to improve my site's PageSpeed. So far so good, I received score of 91 points for mobile and 97 points for desktops using Google PageSpeed Insights.
However, when I add a CDN service for CSS, JavaScript, and images, the mobile score drops to 79 while the desktop score remains at 97 points.
My question is: Why am I receiving a lower core when using a CDN? There are no additional warnings in the Google PageSpeed Insights report page, just that the mobile score drops by 12 points.
I'm using W3TC/MaxCDN pull zone with default settings.