Hi, I have an old used iPhone 6s. Recently I noticed that after charging to 100% and powered it off, the battery won't hold the charge for more then 2 days. 2 days later when I tried to boot it up it will show a dead battery logo and request to be charged. Today(2/10/18), I went to my local Apple Store where they ran a MRI and stated the battery passed with a health of 97% and 107 charge cycles. I decided to go ahead with the battery replacement as recommended by the staff. After an hour, I got back the device with a new battery. I went home and charge it to full 100% and left it to idle for 5 hours. During this 5 hours, the phone was in Airplane Mode and never touched. The battery went from 100% to 70%. Is this still a battery issue or something wrong with the hardware itself? Thanks!