The back side windows have a trim piece under them. It starts at the rear door at the bottom of the windows to the back of the window. It has 4-5 flat tabs that allow water to get inside the rear fenders. Lift it straight up and put some RTV in the holes and replace the trim. This is where I had water coming in on mine.
You may want to check these as well
The picture shows the white clip piece remove it and RTV around that area. My white clip came up during my removal process.