clicking update opens apps, but does not update them

When I click "update" in the app store, the app that should update opens, but does not update.

DEVICE: I am using an ipad mini with iOS 7.0.6 and 5.6 GB of storage available. I don't have any kind of app manager apps or anything like that.

THINGS I HAVE TRIED:

rebooting

closing all apps and rebooting

signing out of app store, closing all apps, rebooting, and signing back in to app store

deleting apps to create more space

changed app store settings to update automatically