iTunes 12.1.2 (and 12.2) cannot connect via AirPlay to Apple TV 3

iTunes no longer seems to be able to connect to either of my AppleTV 3 via AirPlay to stream music. Any attempt to connect via the AirPlay Icon next to the volume slider in iTunes ends up with an error dialog stating "An error occurred while connecting to the AirPlay device “Apple TV”. The network connection timed out." This only seems to be a problem with iTunes and the AppleTV, as the Mac mini iTunes is running can directly connect to the AppleTV (Cmd-click on volume icon in status bar, and choose the AppleTV as the destination of all computer sound output). My iPad can stream music AND mirror to the apple TV as can my iPhone 6. Additionally iTunes CAN stream to my (older) AirportExpress via Airplay without problems. Also, the AppleTVs have no problem seeing the shared music library on the MacMini via the "Computer" app using Home sharing. So I know all the connectivity is correct. I cant pinpoint exactly when this started to happen, but its within the last few weeks. This only recently began to happen.

Full hardware info:

iTunes Host: Mac Mini (Early 2009)

OSX: Yosemite 10.10.4

iTunes 12.1.2.27 (until yesterday when it updated to 12.2.0.145)

Apple TV - Model A1427 - 3,1 software v7.2 (7512)

ALL hardware is hardwired via GB Ethernet - multiple routers, all bridged all within same subnet.

I have tried various things I have seen on the nets, like disabling IPv6 on my Mac all to no avail. I downloaded a Bonjour browser and my Mac mini DOES see the advertisements from all devices. I've exhausted all things I could think of short of totally resetting the Apple TVs. Any help diagnosing and fixing appreciated.