A turkey baster from the dollar store can help troubleshoot suspected sunroof drain issues.
Fill the baster with water, insert the tip into the drain hoses, (one at a time) and inject the contents. The average baster holds about as much water as the i.d of the hose could contain if it was blocked, so a second baster's worth would overflow when added to the hose if the hose is restricted/blocked.
It's worth noting that the front drains are routed into the rear of the front fender area, just ahead of the door. If this area is clogged with organic debris, the drain won't function properly.
Good luck troubleshooting this, and please update the thread so others can learn from your experiences.