You might have sanded through the clear and your looking at UV damage to the base coat. Had that problem in a couple areas on my 41 a few years ago. If that is the case the only real fix that I know of is to sand the panel down and repaint because re-clearing won't help the damaged base coat.
I'm not saying this is your problem but it is something to take into consideration. MARTINSR or one of our other pros should be able to tell you for sure when you can post some better pics.