Messages not updating

I am running 10.8.3 on my iMac, and iOS 6.1.3 on my iPhone 4S and on my iPad 2. For some reason Messages sent from or received on my iPhone do not show up on my iPad or iMac. This behavior started a few days ago. I'm logged into iCloud on all three devices. Why aren't messages updating? I haven't changed anything. Does anyone have any ideas?

Thanks in advance for any suggestions.