I used white marble chip rocks about 4 years ago in landscaping around my house. Since then they have become discolored, dirty-looking, and I need advice on how to clean them without damaging the bayberry bushes that have been planted in them and the surrounding plants in the area. I was thinking of washing them, but the soap may damage the plants. Help!! I can't find anything on the Internet regarding maintenance and cleaning of these chips. Thanks for any helpful hints.