Well that is the power going out to the devices... and if none of those devices are working, fantastic fan, lights, then you have to start looking at the neutral connections. They all have white wires going back to a terminal board, and you could have a problem where the main neutral wire connects to the C terminal.
If you can run a check from a light fixture with the bulb removed back to "C" you should show the 12.7 volts... and you should also show the same across the light fixture from center to edge. If you don't have that voltage across the fixture itself, but you do when you check from positive at the fixture to C, then you have lost your neutral connection, and because everything seems to be lost I would say it would be where there is a connection to your white wire terminal strip.
