I have 4 inch flex tube coming off of each miner that connects to a 4 inch Wye. All 7 eyes are connected to each other in a row and attach to a 6 inch exhaust tube that is insulated flex tube going out of the building.
SO SEVEN 4" tubes all being pushed through a single 6" opening? The problem should be obvious, you dont have nearly enough flow to remove the heat. You are creating backpressure and the miners cannot exhaust properly, hence the miners overheating.