if you have fed too much and your plants are going brown round the edges.
then you need to flush the old stored food,left in the soil/roots, not good.
also you need to flush, when say a plants takes 8 weeks 12/12.
you would start to flush at week 6 to get rid of the food and carbs, from the plants, so it smokes and cures better.
to you need to flush your plants?.