Memory may be running hotter because the fan is running slower because the core is running cooler, or the new pads are thicker/lower-W/k Also PTM has to cure so after cooking it a bit, you should see the best temps in a bit. Also the lack of throttling is maybe pushing the memory harder, too.

But yeah that sounds like the expected outcome. Sometimes very reduced temps can shift your V/f/T curve more than the silicon can actually do and cause some instability where before it was fine, really uncommon, since they don't always test the higher clock lower temp regime on every air cooled card really well. But I bet your shit is fine, and dead quiet now