The only way to have good soil throughout the grow is having organic soil. Chemical supplements destory the microbes in the soil, add salts and other fillers which nature never intended putting in our soil. Building a living soil only requires a little forethought and committment maintaining a soils health. Having a healthy soil allows the plant to grow by breaking down the soil and obtaining the nutes from the soil verses adding chemicals which kill a healthy soil and grows the plant by giving the plant nutes directly to the plant whether the plant is in need of those nutes or not.
With good organic soil I am able to grow my babies from either seed or clone with a mininum of fuss over the soil. Watering with some molasses and sometimes manure tea, I am able maintain a healthy plant, good soil with lots of microbes and other little beasties growing happily in the soil. There is not need to flush the plant since you have added nothing to the soil or the plant which was is harmful to the soil or to the plant prior to harvesting.
Here is a link to Subcool's organics, I don't follow this per se but he has a great concept and use of organics. I suggest doing some research and reading on this subject. I believe you will find it very informative and give you many ideas that you can use in different ways to fit into the way you want to grow.
https://www.rollitup.org/subcools-old-school-organics/
Happy Growing and Keep it Organic