Bag of soil has mold or something on it...?

[logic1248]

My bag of bonsai soil has a green mold or mildew on the inside of the plastic, doesn't seem to have grown on the soil itself and it doesnt even wipe off if you rub it its just like the bag just above the soil line was stained green . I know that the rooting cubes I use say on the package if the bag molds don't worry about it, should I not take a chance and throw it out ?
I used it for a young starter a month or two ago and its fine but I'm not sure if the mold or whatever was there then.