Are you growing with Chemical Nutes or Organic. Organic no need to flush. I flush 10 days out from my projected harvest. Indoors.
Depends. I tend to ramp up bloom nutes towards the end and get minimum amount of burn, the flush always relieves this for the finishing time at the end. That's why I do it. I don't know what is absorbing what, but relieve the burn it does.Flushing is a myth.