iMessage doesn't work for 1-2 people

This started last night. The two people I text the most suddenly don't work with iMessage. It goes back and forth between sending as iMessage then failing and sending as text message and sending as iMessage, not saying delivered, then sending as a text 10 minutes later.

I have an iPhone 6 with ios 9.0.2

I have tried turning iMessage off/on, turning data off/on, resetting my phone, resetting network settings, signing out of my Apple ID and back in, turning the phone on and off and nothing works.