Got back from a camping trip this weekend. Noticed these spots on the canvas tents. Would not come off after washing. Seemed to be a lot of sap on the cars, not sure if that is what it is though.
Not a stain like that, but little mold spots. Over the winter stains may happen if the front bunk gets any water inside. Usually from the way the fabric folds when the door is closed, and what the damp canvas touches. I’ve gotten it all out with some work.