We had the opposite problem, our appliances worked fine at 5600', at sea level the suburban furnace would ' blow out' on lighting. It was a too much air issue which would not let the flame settle on the burner. When the flame did catch, it was loud like a roar, not a hum. So a piece of electrical tape to restrict the fan intake settled and quieted the flame.
Water heaters are often affected by altitude or fuel , thats why they have an adjustable air slide . You can use how they burn as an indicator of other issues that may affect your other appliances.
Fuel is more of an issue than most realize, LPG is not always pure propane, it often has a butane mix, that lowers its evaporation point, which is tied to temperature.
So if you are at high ( or any ) elevation on a chilly night. its possible not enough vapor could boiloff to meet demand if there is butane mix or if the propane bottle is low.