I have a rig which is similar to yours but they are Sapphire.
They never consume more than 750 watts even when dual mining at the highest peak.
I'll suggest you use claymore inbuilt commands for overclocking and undervolting and give it a try.
BTW, you are running from 120V outlet or 230V outlet?
as I mentioned I have no access to them any more, the owner called me for support and I was like what? how is it possible?
For 8 x sapphire pulses which are hashing at 30.2 solo on eth I pull from the wall 1350 Watts max
Let's say 100 watts in being consumed by the system, which makes 1280 watts for 6 GPUs. i.e, 213.33 Watts per GPU which is way above the TDP of the card.
I'm pretty sure it cannot be the case or else GPUs will shut itself down after a brief moment of working.
Moreover, you can still heavy under-volt your Sapphire so that it doesn't consume more than 100W from the wall per GPU, totalling to 850-900 Watts in total.