I've heard many things about efest batteries being rewraps and whatnot but I've been using two of them for probably about 4 or 5 months now and they've always worked flawlessly. I'm only using them on my smpl mod clone by amod and recently I've been getting a horrible hot button when starting a vape session. Like within a minute and it's unbearable. Only doing a .3 ohm build currently. But the main thing I'm getting at is this; I just noticed these black markings on the bottom of my batteries and the contact of the mod itself. The markings are also on the second battery not shown in the picture. I stopped using it immediately after noticing. Any help would be greatly appreciated.