Ability to Defer Parsing of JS For Site Speed

I have all my sites using the Epik theme. Love it!

I have minimal plugins but my site speed is still slow.

In GTMetrix I’m getting bad grades including for parsing of JS.

Is there anyway to add code to the functions.php file where it will properly defer parsing of JS and thus increase site speed and improve GTMetrix scores?

Particularly troublesome JS includes:

wp-includes/js/comment-reply.min.js?ver=4.3.1

wp-includes/js/jquery/jquery-migrate.min.js?ver=1.2.1

wp-includes/js/jquery/jquery.js?ver=1.11.3

Thank you!