i have 5x 280x and 1x rx 470 in one rig.  
my problem is, GPU 5 get low hashrate.
GPU 0,1,2,3,=R9 280x @ 210
GPU 4 RX 470 @ 170
GPU 5 R9 280x @ 32

why GPU 5 get 32h/s . try with different position but still have problem

-mobo asrock H81