If you are using font-awesome via maxcdn there are possibilities your website become slow. The issue is related with MCMC blocked URL causing delay on loading the website which is using the service.

This workaround is applicable to Linux and Windows hosting.

You can check at browser loading status at the bottom of the browser during site loading, if they are url like 'maxcdn.bootstrapcdn.com', this may be related with the issue.

If you find files that use the maxcdn link, you can refer to the link below to get a replacement

https://cdnjs.com/libraries/font-awesome/

e.g. replacement:-

original link: https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css
new link: https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.5.0/css/font-awesome.min.css

make sure the version and link type are the same

css replace with css
font replace with font