I cant use 3 Monitors on my R9 280x why ?

I bought last day 2 Adapters from Mini DP to HDMI, so and know i tried to use 3 Monitors on it.
My first is on 1 Adapter (mini DP to HDMI) and the second is on the other Adapter... but my third monitor is connected with HDMI only and it doesnt work. ?




sry for my bad English skills,, ;D



here is a Picture of the Windows Settings


The Red Circle is the Monitor without any Settings...