You don't have to flush at all during an organic grow, actually.
The reason why people try to flush their plants is because they use synthetic chemicals to feed their plants. With organic grows, you don't need to worry about that at all. Especially if you don't overfeed your plants.
Now, don't get me wrong, there are growers that try to flush their organically grown plants. But, it doesn't do a whole lot, to be honest. And most times people do it due to a possible nutrient toxicity.
Anyway, if your plants look like they are doing fine, I wouldn't worry about it.