Once plants get to a certain stage they practically stop intaking nutes and water anyway, flushing is a waste of time, efffort, and starves the plant. If you want better taste, find different genetics, if you're worried about chemical taste, don't , its just mind over matter.. There is nothing in your nutes that will kill you or that isn't found in nature and the veggies you eat every day...
You can alter the taste by using a bit of mollasses at the last week... I find it leaves the bud tasting like "something else". I personally love the taste of weed itself... No blunts, no chocolate wrappin papers or strawberry... Just give me my weed....