In the bathroom, at the location where I mix my chemicals, there has appeared a green stain on the carpet. Could it have been caused by photo chemicals? It seems to have appeared over time. I used mostly B&W chemistry though I did experiment with an RA4 kit some months ago. Any idea of how to get rid of it? It doesn't want to come out with regular soap and water. And... no, getting a new carpet is not an option.