Nute burn? Ppm runoff

runoff should be higher than what is in the plant, fwiw. it shouldn't be 4000ppm, though. soil runoff will be higher than soilless context. if the nutes purchased require chelation/fixation from microbes, then those things add to teh ppm, but are not being taken in by roots... so you have that excess dissolved minerals in the soil that stays there... takes time for stuff to break it down.. causes higher ppm in soil with "organic" ferts. if soilless, don't flush for minor problems... simply change concnetrations/ratio and give a bit more runoff than normal.. this will transition the entire substrate very quickly to the new concentration levels. weighted average over time.. so if the pot is 25% of weight (therefore roughyl 25% of water volume, you add 150% it's flushing that shit out no problem without starving your plant.. maybe a bit more runoff? doesn't matter the plant won't drown in that time unless you don't have enough aeration in substrate from perlite etc) flush only for EXTREMELY CATASTROPHIC situations... lol... like holy shit it's about to die! otherwise there are way better ways... and those additives for cleaning/flushing a substrate are fucking useless marketing nonsense. runoff will do it just as fast with nothing else added if needed.