I may have screwed up. I was cleaning my Walther PPK/S tonight. I had it stripped down and was spraying Powder Blast on the action. I got some Powder Blast on the plastic grips and it turned them gray in spots. I tried using soap and water, and scrubbing them with a tooth brush. It helped some but you can still see the gray spots on them. Anyone have any ideas? Or do I need to replace them?