Go download an app call accubattery and use it to monitor see which app causing ur phone not getting to deep sleep..
Yeap haha. I turned off everything too (other than the phone)!
The first two days after getting phone I also lost 15%+ overnight, but after that it was okay, average drain around 3% per night. However the past few days my processor keep heating up quite easily, despite rebooting and clearing cache etc. Then last night boom 17% gone.