you still have at least 3 weeks all the plants pistils are white, but yeah no more vert growth from this point and the N pull is fine, add just a lil N to your feeding if you wish but it is not necessary. With the floro to hps the sooner the better if you have the option I would say drop the big light in at 2 weeks old, its not necessary(but also not bad) before that then the plants will have at least 5 days to adjust before flowering.
The plants wont really get any taller except for the tips but that will be due to bud growth. Those white pistils will start to turn orange/ brown and then recede as the second push of pistils comes in. Eventually you will get the third and final set of pistils and this is when the buds will noticeable bulk up. Let them plant for a while longer so the buds and caylxes swell and then chop when the time is right.
You want to harvest when the plant is ready which tends to be a bit later than the seed companies like to say. So my point is read the plant and wait for it to be ready rather than the seed package. It is scary/confusing/ exciting n all that trying to figure it out the first time but there are good pointers in the harvesting subforum, and after one or a few harvests you will be able to tell when by looking at the plants.
But they look good and are coming right along.