Depends on your grow, if you’re a salt grower who feeds heavy it would be wise to cut back on the nutes as you get closer to harvest.
Flushing is considered pouring water 2-3 times the size of the pot.
Leaching is when you dial back the nutes or just give water the last few days ( or weeks) and maintain the plants health. This way the plant “uses”its stored nutrients
People will give quick answers but never take in consideration that every growers environment is different from the next.