Check what the colour profile is set to on output 2 in system preferences/displays

Should be 'generic RGB'
Not the 'Datapath' profile
Apparently the Datapath profile has the incorrect gamma value - so best avoided

Please report any issues with dimness being observed - has been seen on other shows - but is related to Datapath colour profile - not catalyst software.

In some cases the Datapath profile seems to get automatically selected - but not managed to replicate the issue or re-create the scenario where it gets changed...

Until resolved - please check the colour profile settings in system preferences for each display (usually should be 'generic RGB')

S