Did or does it have a toxicity? A hint that too high of concentration of nutes is in the media?
If not, no worries.. Zero need to flush. Flushin does not reduce mineral content of the flower mass... incontravertible fact.
In fact, not that it was statistically significant but quite ironic -- a longer flush resusted in higher levels of magnesium and iron in the flow mass, lol.... it actualyl had a high mineral content, BWAHAHAH. Sorry, i love that tidbit out the research results. But, it was within normal volatility (not statistically significant to resolve as a confident correlation weak or not) that could have just been coincidentally higher but not caused by the flushing technique.
Flushing is a tool. Use it in response to an observed problem.
Doing a flush as you near harvest will not cause any major problems, but nor does it benefit anything, quantitatively speaking.. People that have done it for decades have "faith" in it... they ignore evidence based research and blind taste tests that show what a useless thing it truly is. If you do something for 30 years, it's difficult for many to admit doing so was not helpful and more akin to some OCD tick.
trichomes
pistils
density of nugs
use those three to determine harvest and just do it ... experiment wiht early-to-late window and find what you like. Drugs can impact people differently. e.g. Nyquil will put most people into a coma within 30minutes, but some people get hyper from it. What is good sleepy time buds for one person may not be the same for the next.. or whichever effect you are seeking.