I've had the same thing. It's because my housing was too dirty + my cover was hazed and got so many needle point scratches. I took them appart yesterday evening, clean the housing and sand the cover today. Put them back on, it's great and the outputs are the same again. Check to see if there's a layer of dirt on your housing, they would cause the same problem.

if not, make sure you have both 9005 bulbs in there