I've been using my iPad charger to fast charge my iPhone 7 and it charges super fast. Is buying a new charger necessary for the X or can I use my iPad Pro 10.5 charger? Also, any harm in using the iPad charger on the 7? I noticed if I'm on a call and using the phone while 'fast charging' it gets really warm. I don't do it every night, just when I need juice quick. Thoughts?