I just got Update3 or GDR3 for the 8X and since then I have experienced a great amount of battery drain. Previous to this update I could use my phone on a single charge for 14+ hours with heavy usages.
Since the update with no changes to apps, I am lucky to get 6 hours with standby. Today my phone lost 8% while turned off. Here is a screen shot of the latest charge. Down from 40% to 15% in 2 hours and the phone was off for 1 of those hours as I was on a plane.
Have you searched Google on the issue, The only thing I can suggest is a Power cycle maybe run a cache Partition clear, use to Task killers were known for draining the battery or some apps but as mention you didn't change your app you could do this if your apps need updated.. Update them to the very latest that way they'll work with the latest software your phone updated too