Hello Teagan !
I would recommand a lot of pole on the ground exercises with a little long distances to make your horse cover his strides contract by keeping a active 350, if your canter is more a 325 , you will do a extra stride and will realise that the rythm is not enough. And you will do it again faster until you get your correct stride.
Another exercise, you can so is 3 poles on the ground at 3m each, if your on the correct 350 m/min he won't touch a pole and will do easy strides in, if under 350 the distance will be long and you he will touch the poles , that will make you react to move him more .
A use of dressage whip to reforce your legs and or spurs will also always help ;)