6 GPU Set-up..only 3 work. HELP!!

[new2thisstuff]

Good Evening Everyone!

So today I built my 6 gpu mining rig and I only have 3 working. I will list my specs and my troubleshooting steps I took. I now have a black screen and cannot load into windows (I do load into BIOS with no problem)

Hardware:

MSI S270 SLI Plus
x6 Gigabyte 1070 windforce OC video cards
1200W Corsair HX1200I Power Supply
Intel Celeron G3900 Skylake Dual-Core 2.8 GHz LGA 1151
Ballistix Sport LT 4GB Single DDR4
DREVO X1 Pro 64GB SSD Internal Solid State Drive
Leboo 6-Pack PCIE Riser VER 007 PCI Riser 6 PIN 1x to x16 Powered Riser Adapter Card w/ 60cm USB 3.0

Troubleshooting:

-I upgraded bios to newest version 1.7
-Confirmed window was installed using UEFI
-Made multiple changes to PEG0/PEG1 using GEN1/2/3
-Made sure enable 4g/mining is enabled

I am not sure where I go from here. I tried to go into device manager and install driver one by one, but when I did that and I restarted the rig I now have black screen.

One thing I did not do was plug in only 1 GPU and install the driver and then plug in the rest (first time newbie mistake possibly ). I am thinking my way forward is to reinstall windows and start fresh?? Any help would be greatly appreciated! Thank you everyone!

[Undefined31415]

Have you tried starting at 3 and adding the remainder one-by-one?

[new2thisstuff]

I also have not tried this . I have read many threads on here after I encountered my problem, but I have not seen any related to my board unfortunately. Do you think the best bet would be to install windows again with just 3 plugged in, update all software and drivers, and then plug in each one by one? Also, when you plug in each 1 by 1, should I install the drivers for it, or just let windows detect it?