When do the buds grow the most?

Hey guys, I have 10 plants that are 6 ft tall of the Snow White strain. They are under a 400 hps and are now in their 7th week of flowering. I am just noticing that a few of the hairs are starting to turn orange. I'm a bit concerned because it doesn't seem like the buds are that big yet.

So my question is this. When do buds grow the most? I heard it's in the last two weeks. How much bigger are we talking?

My buds normally start packing on the weight and girth from the middle of the flower period all the way to the end. You still have 1-3 weeks left so lets hope you get some more density