Every once in a while, the App Store seems to glitch out and get stuck either not properly updating or not showing new updates correctly. Over on Twitter, Zachary Drayer points out that you can force reload everything in the app by tapping an icon on the tab bar 10 times.
All you need to do is tap any of the five menu items at the bottom of the App Store screen 10 times in a row (you'll need to tap the same one 10 times). When you do that, you'll see the screen briefly go blank and reload everything. If updates aren't properly showing or if something's stuck, it's a good way to try and get things moving again.