I have recently Updated my Drivers... previous to 18.2.4 all three of my monitors were working correctly. I have two rx570 RoG. I have checked device manager and noticed one card had an error. After a clean install The error has gone away, yet only one monitor works correctly. Device manager shows 2 cards. The ASUS Gpu Tweak shows one card as a rx570 and one as a STRIX RX570.
Previous to install of new Drivers