my six vega rig in which all gpus are running at 50 to 65 degree C
hbm memory will crash at the temps you are running your gpus
ramp fan speed to 4000 rpms
I ramped fan speed to maximum and i still get high temps, I added extra vent to cool them down.
Would you please send me you WattMan or afterburner settings?
maybe the problem can be you did not undervolt the cards much
which means that they consume a lot of power which is not needed and in turn convert it into heat
i will recommend checking reddit post vega definitive guide for mining
everything is available on that post and that should help to reduce temps