3rd GPU mining at lower hashrate?

[Pixelhouse]

Setup:
ASRock 970 extreme 4
4x r9 280x royalqueen
1000w
Win7 x64

So i have 2 GPU's currently running on a powered 1x to 16x riser cable on the 2 x1 slots. Those work perfectly.
The problem starts when i plug in a 3rd GPU in the first x16 slot.
It reads the card and shows up in device manager but while the first two mine at 730Mh/s the 3rd GPU mined at around 180(also on powered x1 riser), same problem when i connect it directly to the MB.

Did anyone have the same problems?
http://www.4gp.tw/b027/1389677985920.jpg

http://www.4gp.tw/b027/1389678174386.jpg

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[animekub]

Have you tried plugging in the monitor to the one on the 16x slot?

[Pixelhouse]

Have you tried plugging in the monitor to the one on the 16x slot?

No i have not its currently plugged into the first x1 slot. I will try that as soon as i get home.