pingdom connection error

Hello, I am using generatepress with 4 sites. One of them gets a connection error on pingdom.com. It reads: http://samanka.paprsky1.com/wp-content/themes/generatepress/css/defaults.min.css?e0736d. It seems that this makes the page to load about 2 seconds longer. Does anybody have any idea what it is about and how to solve it? Thanks a lot Jirka