my Iphone 6s Plus had about 74% battery capacity. somehow overnight while sitting on the dresser doing nothing it dropped to 63% which is very unusual. **Usage 4h,31 mins- Standby 36h, 7 mins. No WiFi/Data was on. No notification/ Everything else could drain the battery is disable! When I checked the battery usage screen it says the home & lock screen used 85% 15 mins on screen. - I reset it once, still the same , im on 9.2(13C75) Now dropped to 61%. *Usage 5h,3 mins- Standby 39h, 4 mins. i don't know what to do to fix this. culd be battery defect or what , pls help!