Then one day they all suddenly had HW faults of .0005% or higher. A chain on each S9 suddenly had thousands of HW faults. This all happened at the same time on all of my S9's
Since my units in Oregon and Colorado are on completely different power grids and internet the only thing they have in common is the pool.
So I do think the pools can effect HW faults.
This is just my opinion.
I think you are right, mine went up all at the same time on Slush. I moved from BTC.COM because of the same thing 3 months ago, now i got it with Slush and im back at BTC.COM.
Cheers