They all have the same: Hardware, OS (Win 10), BIOS version and settings, nvidia drivers, risers, miner & arguments.
The only difference I found between them is that in the low performing one, GPU-Z shows 3.3GB under 'Memory usage (dedicated)' vs 480MB on the high performance ones. Virtual Memory is set to 35gb on all.
There's a 5-10% difference in performance, doesn't matter which algo or miner is used.

Not sure where else to look.