Shorter than normal internodal spacing and smaller leaves
woodier stems
brittle stems
Those were terms I think Storm Shadow used that helped me identify my duds.
Just curious can duds spread from plant to plant or just from mother to clone? Back in the day I sprayed a plant with colchicine and it permanently ruined the plant and all succeeding generations of cuttings. So if someone passed out cuts from a colchicine treated plant it would grow stunted.