Yours will probably grow bigger than mine because mine got sick for a couple of weeks before flowering, I almost drown them and then they got nutrient lock out. So I'm sure as health as yours are they will get bigger. I have heard when they start flowering they should grow double or triple in size.
Not much, mine went about 30 days before pre flower. I think I prolong mine from budding because I topped them so much. But they didn't get much bigger. I also cloaned the northern lights and when it got rooted it shot out a bud, so crazy. Have you ever cloaned an auto? I've heard they won't...
I do it about 2 weeks into budding, then about every other watering. I can see the crystals a day or 2 just piling on. Expeirment with one of your plants and compare it, I think you will be happy with the results.