When I brush my tongue, it is a nice pink color. Anytime I eat something the back 2/3 gets light coating, but the front 1/3 about the size of a dime never stains or coats. I can eat or drink anything but that part, about the size of a dime will not stain. The only way I notice this is because the back 2/3 always coats. Is it abnormal for the front 1/3 to not coat or stain at all, even after drinking red Kool-aid? I don't have any pain or discomfort or any other symptoms, lumps, discoloration, etc.