They couldn't quite make it a double in 2018, placing sixth in the under-20 double sculls final.
Cox picked up a second medal on Lake Karapiro, claiming bronze in the women's under-20 single sculls.
Cox finished 13 seconds off first place, taken by Canterbury's Veronica Wall, with Auckland's Alice Grave claiming silver.
Brooke and Cox weren't Whangarei Rowing Club's only medallists at the premier rowing event.
Women's novice double sculls pairing Linda Schoeneborn and Yvette Hendrikse grabbed the bronze medal in a tense finish.
Cambridge's Holly Williams and Madison Fuller grabbed the gold but it was the battle for silver that excited the crowd.
Racing in lanes five and six, Schoeneborn and Hendrikse were neck and neck with Waikato's Katie Lush and Laura Hutchinson right to the finish only for the Waikato pairing to pip them by just six-tenths of a second.
The pair also won the B final in the women's club double sculls.
Kendall Smith had a strong week at the competition, finishing fourth in the women's senior single sculls and fifth in the senior coxless pair oars (with Brooke).
Whangarei Rowing Club carried form into nationals from the recent North Island Club Championships.
Cox picked up a gold in the women's senior single sculls and bronze in the under-20 single sculls.
Cox and Brooke gave a glimpse into their national win with the North Island title in the women's senior double sculls.
Meanwhile Callum Bolitho earned silver for his place in the A final of the men's intermediate single sculls at the North Island Club Championships.
Schoeneborn, Hendrikse, Lana Newman and Heather Nichols took bronze in the A final of the women's novice coxed quad sculls with cox Aaron Harold.
Lucas Gardiner, Bolitho, Rhys Paget and Calum Sapwell, coxed by Aaron Harold, placed first in the B final of the intermediate men's coxed quad sculls.
Letty Hamlet coming second in her A final of girls' under-17 year single sculls.
