iOS 8 third party keyboards are broken

I tried installing three different 3rd party keyboards, Swype, Fleksy and SwiftKey. All of them appear broken with either an invisible keyboard, or a grey background and no keys present. Tapping in the keyboard area doesn't produce any typed keys. All three were downloaded from the app store and then installed through the settings app.

When I switch from the standard English keyboard to any of these three keyboards (using the global key), the keyboard appears as a solid grey background with no keys, but the app acts as if the keyboard is activated. If I close the app (double tap home button, swipe up to fully close the app) and then reopen the app to type something in, then the keyboard appears invisible as if the keyboard never animated up from the bottom of the screen.

This happens with all apps that present a keyboard. If I want the English keyboard back, I have to go into the settings app and remove those third party keyboards from the installed list. Restarting my iPhone with and without the keyboards installed doesn't seem to fix or improve the problem.

here's a screenshot of a broken keyboard in the Notes app: