questions about harvest

i have a ways to harvest but i like to be well informed,
so i would like to know about

1. i hear about 48 hours of darkness before harvest? or something like that can someone clear that up for me

2. i see that most plants take about 8 weeks or so for bloom, now is that 8 weeks with nutes and then 2 with clean water? or 6 with nutes 2 without

3. when i start using clean water does the plant still thicken (nugs grow a bit)

4. once i use clean water ( i filter it with a stealth RO) do i need any kinda nutes or cal-mag or anything at all?

48 hours or 24 IMO makes the plant give that last little bit before her death, its a good thing.

as far as weeks go, get yourself a jewel scope or loupe and use it to look at your trichs on your plant. If you watch and harvest when the plant is ready instead of the calendar, you will get better buds IMO

depending on what is left for nutrients in your soil will depend on how big your buds grow, they still need some kind of nutes while growing.