It looks like some Google services or system processes are draining battery. This is quite tricky: it can be sync services (unless you turn sync off globally, turning off internet connection does not turn off these services), it can be calendar services, it can be location services… Unfortunately, after Kitkat update, it is harder to identify unless it is rooted.
For such issues, reboot is usually not sufficient. Sometimes, you need clear the cache partition.
If you can replace the phone without additional charges, I would recommend you to replace it.