Athosanswered grow question 7 years ago See those leaves with a claw like shape? That's nutrient overdose. I would flush the media and let the plants consume what's on their leaves for a week before starting nutes again. Also get a PPM/EC meter, that will help a lot in how much to feed without guessing, specially in a micro grow when a couple of drops can put the feeding strength from ok to too much (I do microgrowing too).
And to answer your question (if you didn't have nute overdose), you would want to keep using the grow nutes until the stretch is done and start the bloom ones between the 2nd or 3d week of flower, when you notice the first signs of P-K deficiency on the lower leaves.