Quite simply, the battery is defective, and Apple will replace it free of charge if your iPhone 6 is under warranty.
It's not always doom and gloom.
Phew, thanks I am happy it's covered.
One other annoying thing I noticed though which I hope you know something about, is that on the top left corner of my screen, it's dimmer, like a faded area and it's getting bigger and bigger, it's not major yet but it's starting to be annoying as when I film or take pictures I can always see that upper left corner being dimmed. Do you know of any issues like that with the iPhone 6? I'm hyper sensitive when it comes to handling my phone so it's not seen brutal usage. It's the 128GB iPhone 6.