I have the ac set to have the house at 67,
Holy cow, you keep your house like a refrigerator! My AC is set to 78*, it would run 24/7 for almost the entire year at your temp! Hell, my
heater comes on at less than 73*...
not sure which would keep the miners cooler blowing air at them or removing the heat they output.
Priority 1 should be to remove the hot air, cool air supply should be #2.