I clean Porkchop's nose rope every evening with a water and vinegar mix. Lately there is a large amount of black/brown gunk coming off the cotton pads. There is no odor. He is fed dry Wellness salmon kibble and I thought maybe this was residue from his sloppy eating. He has been scratching at his face more often. Is it possible to tell whether this is a yeast infection? If so, what do you treat it with? I just read one thread that recommended witch hazel as a good cleaning agent. Maybe I should change to that? Any advice is welcome.