MOORE, Okla. (AP) Like her young "Diff'rent Strokes" co-stars, Dana Plato had seen her share of troubles since the show was canceled. They finally ended not with the happiness she sought, but with the fatal drug overdose she feared. Ms. Plato, 34, died Saturday after apparently taking the painkiller Loritab along with Valium while visiting the home of her fiance's parents. Dr. Fred Jordan, the state medical examiner, said an autopsy showed no evidence of injury or any significant natural disease. Toxicology studies are expected to take a week. [continues 396 words]