A few weeks ago, my phone's battery started draining really quickly; it used to last 5-6 hours of screen on time, but now, it dies before it reaches 3.5 hours. I usually keep my screen < = 25% brightness. I updated to lollipop a few days ago, and that did not have a difference on the battery life whatsoever. What could be causing this, and how can I fix it? Thanks!