First of all, this is just a user forum. No one here is linked to Android development directly. Not even the admin or mods. They may have no idea on what the issue really is if there is a problem with the code.
Second, it is really ideal to factory reset after major updates and start the app installation and setup from scratch. The changes in the code are under the hood, and any previous customization the user made using older app versions may conflict.
I don't think it has anything to do with that.
My battery did same thing. Fully charged at 4.3V at 6:30 AM, down to 4.0V by 9AM. Without all that much usage. I have noticed that my battery life has gotten worse since November when I got it.
I think it's just wear on the battery. It's too small to begin with.