Comment # 1 on bug 1208645 from Stefan Dirsch

Hmm. Feb 14. This was when the repository was updated from 525.85.05 to
525.89.02. Later updates only changed G04 drivers, but you're using G06
drivers. Thanks for the logs. This looks all pretty good.

I'm not familiar with the KDE's monitor configuration tool. And I think
nvidia-settings only work when you have  one nvidia card. I suggest to try
configure your monitor layout with xrandr instead.

# force redetection
xrandr --auto

xrandr

Attach the output of 'xrandr' after running 'xrandr --auto'. If all monitors
are detected you can make the setup manually via xrandr command.