Assuming temperatures are in proper order and the voltages aren't miscalibrated, looks like memory artifacts to me.
Though more often than not, it's not the memory chips which are faulty but their connection to the PCB. If a warranty return is not an option, baking the card to reflow the solder can fix the issue for at least a few months -- and the card can survive being baked more than once.
That said, baking's a last ditch endeavour. If anyone has alternative suggestions I'd try those first.
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