What week of flower do calyx really swell?

I am currently on day 1 week 5. I figured about half way done with my grow. What week do the calf swell?

I would say it's pretty much strain dependant.

Preflowers swell first - shouldnt be hard to see....

They swell with end maturation, usually week-8-9 onwards.

Where do people stand on lowering nute levels during this phase?. I suppose the idea is that X reduction by then is enough for the final phase (any opinions on the acceptable ppm at that stage?). It's one of things you do as a generally accepted good practice but you know, is it right.