 So maybe a mold, so that would take me to that wet-and-forget disinfectant and mold killer. Okay. You could also, you know, I wouldn't do my whole wall with it, but if you just took some straight Clorox and just sprayed that on there, just in one or two spots to see if it fades and disappears, that would be a telltale sign that it's some sort of fungus algae or mold. So that's one guess.