giving a proper amount of fertilizer will never hurt the plant. if it isn't toxic in the rootzone, it's fine to add more.
think about a plant outside. does the roots being sorrounded by nutrients through the end cause problems? No, because that's an insane extrapolation of people that didn't have any education on the subjects 50+ years ago and mindlessly following the blind today. lots of examples of the blind leading the blind in this hobby and it's tied into personality so they take it incredibly hard each time some nonsense is proven to be wrong. just look at the people that "schwaz" as another example or any kind of mass defoliation with the reasoning given as "it forces the plant to focus on buds" - absoutelelyfalse statement and the opposite is treu. if there is a defiit of leaves, the plant will want to grow more leaves unless deep into flower, which is even worse because it can't re-grow what it needs, lol.
flushing has no effect on the constitution of the flowers. they are made the same way according to genetic instruction not based on how much of any one element is stored in the plant. the plant cannot excrete excess, so if there is not a toxic buildup inside the plant currenty, then it's fine.
if the plant is experiencing a deficiency, more building blocks won't hurt and may even help. The good thing is regardless of what you choose to do, if very close to harvest it'll have a minimal impact on result.
flushing is a reaction to a toxicity that has already built up in the root zone and ignored for a period of time long enough to warrant a flush. flushing is incredibly sterssful for the plant and results in temporarily slower growth more times than not. it is a reaction and a cause to an intended effect.. not some magic mumbo jumbo about good tasting buds and reducing mineral content of flower.. that was a weak hypothesis to start and shown through scientific testing to be false. end of story.