Batteries discharging

I would guess that something is not actually off. Your CO and propane detector cannot be turn off so they are dragging down the batteries. Mirror heat is something that some owners forget about and leave on. If your inverter/charger is left on, it will drain the batteries in a few days.
You can put a meter on your battery leads and see how much power is being drained but I suspect that it will surprise you at how many things are still drawing power even tho you think everything is off.