My Ipad 4 won't hold a charge. It was fine for the 1st month of use, but yesterday it started draining with regular use. I keep it plugged in, checked the connections, changed the location of the plug and nothing helped. All locations charge my iPhone 5 just fine so it must be the iPad. This is the 2nd iPad that this has happened to. Any suggestions? (I keep the ipad in the case with no damage, no water spills, no over heating, etc....just regular use).