Placing an advert in your banner especially when it is javascript can slow down the loading of your page. You can try async:
Source: W3Schools
It will then asynchronously execute while the rest of the page is being parsed. I think currently it is waiting for the JavaScript before loading. You can monitor page speed in Google Analytics and that might help you identify, look back at the page speeds before you put the adverts in. You can actually make Google generate asynchronous Adsense code for you to put on your website. Read the Google help section here.
