Just like when flushing before harvest, when your plant suffers from overfeeding it is essential you remove the excess nutrients in the medium and in the roots. To do this, you need to flush with pH water (5.8-6.3 for soil) 2 times a day, ideally, you would water until you see run-off coming from under the pot and repeat it after 15-30min. If you want to make sure you're doing it properly, you can measure the PPM of the run-off, this way you'll know when you have washed off the nutrient excess.