I WENT TO MY BOOT AND FOUND A LUXURY SWIMMING POOL WHERE MY SPARE WHEEL IS,I'VE CHECKED THE REAR LENSES AND THEY SEEM TO BE WATERTIGHT,IF YOU RUN A HOSE OVER THE CAR CAN VISUALLY SEE WATER COMING THROUGH THE LENSES OR DOES IT TAKE TIME?MY96WRX WITH BUILT IN POOL?

 

Could be the seals between the spoiler & boot perished.

 

Check the seals in the rear lights