2000 Cadillac EL Dorado water on rear passenger floor mats

The front drain tubes run down the A-pillar, and exit behind the wheel house liners. You can flow test them with a bottle of water poured into the tray, clear the with air if need be.

The rear tubes come down into the trunk, just forward of the wheel houses. You will probably have to remove some trunk liners to get a visual on these. Check that they are not draining into the vehicle. Clearing them is a bit more difficult, you would need to lower the headlining to access the top connections. You should be able to check the lower exits for debris, there is usually a pinch valve at the end, and that orifice often clogs. This information is assuming a factory sunroof, if it is aftermarket installed it could be different.