Lightning cable contacts arced and burned

I've had my iPhone 6 for about a week now. I plug it in every night to charge, just like I have with all of my other phones. This morning I woke up and the phone was still at about 25% charge, though it had been plugged in all night. I took the lightning cable out ant noticed that there was some significant black marking and pitting on the contacts, which looked a lot like what happens from electrical arcing. When I took plugged it back in I got the "this charger isn't recognized..." warning. I tried again and everything seemed to work, but this has me concerned.

Pictures of both sides of the connector: