The Plymouth diver, who has won three individual bronzes during the series, had to settle for sixth-place in a high-quality final in Canada with a score of 330.20.
The event was won by 14-year-old Chinese sensation Qian Ren, who scored a staggering 429.35 points to finish 51.45 ahead of her team-mate Si Yajie.
But Couch is the overall leader of the event, sitting four points in front of Canada’s Roseline Filion and six ahead of China’s Roulin Chen. Fellow Plymouth diver Sarah Barrow is ranked seventh.
Meanwhile, Plymouth-born Tom Daley picked up another medal, taking bronze in the men’s platform event in Windsor.
Daley scored 511.50 to finish behind China’s Jian Yang and Yue Lin.
Daley, who also won bronze in the mixed three-metre synchro with Alicia Blagg the day before in Windsore, goes into the final series event ranked second overall.
MORE DIVIING STORIES HERE http://plymouthsportsgazette.com/category/aquatics/