Why does my iPhone 4 battery drain overnight?

This only happened as of recently. I charge my phone at the end of the day and go to bed with a full charge. When I wake up 7 hours later I'm down to about 70%. In the past I'd wake up with 95% or 96% left.

The only applications that are open overnight are phone, clock (alarm), messages, and music. Almost all of my notifications are off except phone, messages, and calendar, and location services are off except find my phone.

I'm running version 5.0.1.

Any ideas?

Thanks