Good evening, I’ve got to clean these sky light bits on these panels not the whole panels just the bit where the light will come through I went and done a test patch today as you can see in the photo, used a detergent in trolley but I’m thinking I need something stronger in there as I wasn’t really making a mark on it I never really use chemicals except tfr or a detergent as I’m mainly doing windows any recommendations on what will shift it with relative ease? Cheers.