Hello Ramgi, usually 1 week before harvest. At the beginning of your last week you have to stop using a fertilizers, wait than day or two to dry a little your substrate and flush with water (water should start flowing from bottom of the pot) next wait two days and repeat flush. Water should start to change a colour to brighter as the residual minerals are rinsed out.
Nothing scary 😃 you will find your preferred way soon 😉
I hope this is helpful.
Happy harvest mate 😃☺️