If you open your sunroof and look arounf the frame assembly you should see 4 drain holes. Two are at the very front of the sunroof recess at the corners. The rear drains are at the rear corners of the sunroof frame, usually we remove the sunroof so that we can see the back area of the frame assembly. From each drain run hoses that direct the water to the bottom of the vehicle where they drain on to the ground. The front hoses run through the front pillars of the windshield,(called the "A" pillar) the rear hoses run down either the middle door post,("B" pillar) or the rear windshield pillar("C" pillar). sometime these hoses disconnect from the drain fittings and cause leaks. It sounds like yours might have debris plugging the rear drains. I use heavy wire (more like braided cable) to clean the drains, the cable is firm enough to push the junk through the hoses. You must be cautious trying to clean the hoses out, if you push too hard you may disconnect the hose from the fittings and to repair this you will have remove the headliner to access the hose and reattach it to the fitting and that is lots of work. Good luck.