Fan speed problems 6x RX470

My setup:
Windows 7 64bit
Six Gpu - AMD Radeon RX470 4GB
Crimson 16.10.1 drivers
MSI Afterburner. Just using to set my fans manual to 75%, no overclock.


Trying recovery wpa password, with all six gpu fans 75%. 
But problem is after wile some gpu jump to 100%, some to 0%. Its not happening with one gpu, its happen randomly sometimes GPU1, sometimes GPU4.

Already fighting all week. And still not solve my problem.
PC turns off if one of fan goes to 0%. 
Please can someone help me?