I, and many others, have had a problem for over a year when in Eyefinity mode, side monitors (or any extra monitors other than the prederred display) would not go to proper sleep mode (blinking or orange power indicator) and instead they just show blank screen with backlight .
This has happened since 17.7.1 and was not fixed even with 18.6.1. With 18.8.1 (and maybe 18.7.1) this has been fixed for me.
I hope anybody with this issue try the 18.8.1 drivers and post here if the problem is fixed for them too.