Display Config. in Manjaro Qonos/KDE Plasma not detecting my 3-monitor set-up?

Hi all,
I have the Manjaro Qonos desktop with KDE/Plasma installed on my ASUS laptop, connected to 2 BENQ 24" monitors.
The display config. menu will only show my laptop monitor.
I have not configured multi-monitor set-ups in Linux before, so would appreciate a bit of advice on where to start.