do you know what happens when you run mass amounts of water over a soil with nutrient pellets in it? that's first off. second, forget the word flush, that is a stoner thing made up by stoners and continued by stoners.
Now, OP, do you have drain holes in those containers, and why are you using clear containers? roots don't like light.
but the real problem is that they are to young for that hot ass soil which as stated is not good for MJ. If it were me, I would try and transplant them into something better. But that's me. new soil, new pots