if you unplug the outlier cards from the graphics card, is the problem still unresolved, with standard reconfiguration options?
Is it only ARMA that exhibits this behavior? If so, do you use a shortcut to launch Arma that has custom launch options?
I don't remember much nvidia junk, with AMD you can set an individual graphics profile for each program or game. Is this the case for you?
Do you use the same control path ( DVI, Dual DVI, HDMI, Display-port) across all monitors?
Are the same make and model?
A screwy thing that happened to me with multiple monitors was that the dual display was messed up because each monitor, under its OSD menu was set to auto-detect the connection type, Both had DVI cables, but one refused to switch resolutions. I had to switch from 'auto-detect' to explicitly setting the connection method, and then it was fine.
I dunno. This is called 'throwing crap at the wall' triage.