When I commented earlier I thought it was just a bit of condensation.Having read that you powerwash your car, due to the high pressure of the jetwash it could have forced water into the light. On a really warm day the condensation should dissapear. Once dry when washing the car next time try not to use a jetwash as its quite a high pressure and theres a possibility of water getting past the seals of the car, top of the bonnet seal,door seals etc and headlights as i said i think but not 100% sure that they are vented. I have always used a hosepipe with a normal spray (not high pressure at all.)Then use either a good quality sponge uncontaminated by that I mean no tiny bits in as they could scratch. Or a washing mitten and a good car shampoo say Meguirs gold class and rely On you washing the muck off rather than rely on water pressure to wash the muck off, And when spraying the car with the hosepipe always spray in the direction where water ingress will be minimal for example the air vents On the wings I would spray water from the front facing the rear of the car. Also to washing the headlights and front section I would spray water On the bonnet facing the front of the car so it runs off and over the grill and lights. The lower part of the front I would again use the hosepipe avoiding high pressure, there is usually if you use an attachment various sprays on,set it to a fine spray this will soak the muck and will easily come off with the sponge Or mitten.
I hope this helps and you get the light sorted
Regards Fred.