BTW, you said "turned off" your phone at night. Sounds like you locked the screen (pressing power button), but it continues to run in standby mode. Shutting down is holding the power button until the popup menu lets you Shut down, Restart, or enter Airplane mode.
Recommend you download SystemPanel or SystemPanel Pro (I find the pro version is worth the price for the extra functionality). The monitoring function (um, that may be one of those Pro features) lets you see what programs are consuming CPU cycles, how much, and when.... Very easy to look back over 8 hours in the morning and see if, say, CattyWumpus for Android, was pegging CPU to 10% every 30 minutes overnight, or if WackyWeather left itself running with 5% CPU utilization all night long. Don't use their "kill" function, Android generally takes care of apps when you run out of memory. But apps which continue busily operating overnight maybe should be uninstalled.
After you've identified the apps that were causing trouble, something you can do at night is to restart the phone (hold down power button until the popup menu appears). This will get clear out apps and some data and such. Just good housekeeping that some support reps continually recommend. It would certainly get your phone ready for the next day as well as closing any apps you don't need while you (and the phone) sleep.