Since upgrading my phone to the latest OS on the Note 4, about 30 mins of Spotify will drop it down to around 88%, maybe less if I use the phone. Anyone know what I can do?
By that you mean marshmallow correct? IIRC it needs a couple days to optimize apps (probably not the best choice of words). During that time it will be using system resources and battery power more than normal.
x2 on the factory reset. I had to do that and once I did everything just fell into place.