Hi,

Sorry, didn't study your post too carefully, so you may or may not want to take my comments seriously, but if you are still under warranty for your notebook (and battery?), thinking you may want to consider looking into this option later too if you can't find an easier solution.

If you want to look into warranty service (or a possible bad battery?), you would probably need to or may want to try putting everything back to how it was originally if this isn't too much trouble just to confirm none of the changes were related to these issues.

I'm ignoring the possibility of software-related causes right now though assuming that if all the N550JK notebooks had this same software issue, ASUS would know about it and more people would be complaining, so theorizing the problem may just be isolated to your unit.
If it's a hardware-related issue, try to get warranty service if you're still covered and if it's a software issue, you may want to reinstall the original ASUS Windows image (and hard drive?) if necessary to check this.

Good luck and hopefully others can provide better suggestions, but just wanted to run these ideas by you.