Just got my iPad 12.9-inch Pro Decided not to use the included USB-C charging power brick. Reason being, I have a really nice braided Anker 6' USB-C to USB-A cord. So I am using the older 12W charging bricks that came with prior iPad Pro models. My new iPad pro seems to charge much slower. Additionally, when using the iPad while plugged into the charger, it loses charge rather than keep it. Is there any difference in the rated power of the prior 12W chargers and the new USB-C chargers included with the new iPad Pro?