This happened after you upgraded from 6.1.3 to 6.1.4 or...
Because I had battery issue a while ago and I thought it was the system as I didn't change any about the way I use my phone. However, turned out, it was because of the updated Facebook and facebook messenger app. I'm not sure what's wrong with the new version, but they seem to use a lot of battery when it's running in the background. If you are using Facebook or Facebook messenger or both and have updated it, that could contribute to the issue you are having.
After I started to kill Facebook and Facebook messenger in background after every use, my phone's battery life now is back to how it was before. Couldn't be happier! If killing off your background processes doesn't help, you might wanna take it in for service.