2015 Airstream Interstate Grand tour Coach battery drain

[hdmike]

Hello, I was hoping someone has some ideas on how to trouble shoot a battery drain issue. My new (7month old Life line batteries ) batteries are at 0 over night with nothing running. I thought it might be the fridge but switched the fridge and freezer off and in the morning the batteries read 0.. Also one thing I noticed is that the main cabin switch by sliding door light doesn't go off when you want to power down the cabin!!
Any ideas or starting points
Thank you