How are you using your rMBP? In other words, what are you doing with it now that you didn't do before? If your computing habits haven't changed, you can always take your machine to Apple and have them check it out since it's still under warranty. An update should have no impact on battery usage.
All of a sudden, my new (as of Feb this year) MBP retina is burning up battery power pretty quickly. Has anyone else experienced this recently? Some kind of software update doing this?