do outdoor plants get flushed? do the nutes in the soil outside cause a problem if you dont? no, of course not.
it absolutely doesn't matter if it is so called "organic" or "mineral" fertilizers. it may impact how long you can go without fertilizing and a starved, decimated canopy. decimating teh canopy does not change the flavor of the flower, lol.
if not overfed you can fertilize to the end - do apply common sense. if in soil, you can be lazy and give water-only irrigations and save some effort for up to 2 weeks - again depends a lot on your previous feeding habits. soilless might hold up 5-7 days of water-only.
so, don't ignore and toxicity symptoms and do react to them accordingly.
if you do start irrigating with water-only and the canopy degrades too fast, you can always give it some more fertilizer, too. It'd be really hard to screw this up as long as you apply common sense to waht you observe. don't over think it.
if it's a toxic mess, do flush the substrate, that's the point of flushing... diluting the substrate. you cannot dilute what is already in the plant. it has no excretion system. flushing won't affect that but will help slowdown whatever is built up from entering the plant.