Paa jee, gari decontaminate karo...tay nalay kuch abbrasive jaya wi karo....here at DC if thr dryin towel gets a stain on it, an investigation is launched as to "why dirt came off a washed car?"......so first sign, improper washing, second sign, contaminants.......my best shot would be, wash, clay, wash, give it a shot with cleaner wax or rotor it with a good abbrasive. Should get you a smooth clean finish.