I've noticed significant battery drainage recently on my iPhone 7 Plus. I took it into Apple cause my receiver sounded muffled and low, it turns out it was just dirty, so they just used a brush to clean it and it sounds significantly louder. Anyway, they ran a battery diagnostic on it as well and it showed that my battery health is at 91% and decreasing faster than it should be. The employee said basically this meant that when my phone says it's at 100%, it's really at 91%. They would not replace it however because it hasn't reached that critical point yet. The woman said it could be from using an iPad charger to charge it but Apple's website says you can do that. My warranty is up in November. Do you think I should just go back and see if another person would do something different?