Flushing, if any, depends on your personal setup (mostly medium and somewhat the nutes you run). Not to jump in and contradict 01011 with science as is customary at this point, but flushing naysayers are the best because they out themselves as being either a lazy bum, uneducated on the plant, or bad at cultivating...all of which you should generally steer away from.
The only arguments against flushing are:
1. Some rando tomato farmers on TikTok saying crap like, 'we dont flush our tomatoes har har gotemmm' which is true but also I don't smoke tomatoes...so, ignore those types for sure. Pure laziness and complacency.
2. Folks have had/heard about good non-flushed runs and bad flushed runs. They lack the ability to dig deep into the mechanisms behind the scenes, pinpoint the source of variation for runs, and so on. To this point, I simply say that you'll find gas in ditchweed if you look long enough. We want repeatability and science over here. I'd also point them towards free salt cycles in the plant, which has direct implication for flushing...like what is the point of just throwing it in water? If you see a bump at night, cycle that flush water. If you're flushing for removing nutes, use an additive. Same cycle implies severing the roots immediately during mid-dark period for an utter minimum of nasty stuff in your flower. Add in a controlled fade, and congrats...you're now one of the top 5% of homegrowers whose flower folks actually wanna twist up.
For me, I flush because I assume abundance if I cannot discern a deficiency, right? I mean, what would be the chances I somehow hit the exact amount the plant wanted? Not good. For that, and cleaning my hydrotek for a 1 hour turnaround on cut, I flush every run. I take the flush further from a nutrient uptake solution to a metabolic focused one if needed depending on the flower structure, steering the fade.
There is this one scientific study with a poo pile of a n that claimed to have debunked flushing. That paper was written by a company that claims to be able to spin up any cannabis research project you want, which is basically a puppy-mill version of cannabis research with old cuts, poor measuring, no statements on nuance, and definitive statements like claiming flushing is a myth whilst the majority of growers swear by it.
Unflushed weed is bad for your health. Fact fax.