Around midnight I plugged in my S6 Edge+ with about 25% battery life. When I woke up at 7AM, it had 74%. It's now 9:30, and is only at 86%. It's plugged directly into the wall with the adapter and USB cable that came with the phone, and hasn't had this problem before. I thought maybe the power had gone out during the night, but that doesn't appear to be the case. Any thoughts as to why this happened suddenly?