The reason there is extra space in those particular widget areas is because they both are set to 45% width. So if the featured posts widgets are only 300px, and the widget area that it’s inside of is 45%, then there will be extra space since the widget area width is wider than the fixed widget (300px). You can change the featured post widget width to 100% if you want it to fill the entire widget area (home-feature-1 and home-feature-2). Hope that makes sense.
