My iPad 2 has recently become VERY slow to charge- about 1% every 10 minutes while plugged into my Retina MacBook Pro (my usual charging source). I've tried both USB ports on the rMBP and neither seems faster than the other. I checked the Apple support website and it was said to be a bug in iOS 7, but my iPad was charging fine for a few weeks after I updated. What could be some possible causes of this.
NOTE: the battery drains at a normal rate.