I was Wondering... :3
The Striaton City Gym. (Cilan, Cress, and Chili) was replaced by Roxie.
The Irricus City Gym. (Brycen) was replaced by Marlon.
Hope This Helped :D
The Triplet Gym and Brycen's Gym(1st Gym and Ice Gym) but they dont replace them in that order.