I grew BK on my first grow too.
IMHO you gots several weeks to go. Mine got pulled early but at a much later stage than yours are at and I can only imagine how amazing it would smokes with another 2 weeks.
You want at least 90% of those pistols brown then need to start checking tricomes with a magnifying glass or similar. Once they are mostly milky then its up to you how much longer you wait. For BK if you let trics go mostly amber you will probably get stuck in your seat.
Lol you gotta love that frost, you are definitely at the hardest stage of growing. The last few weeks before harvest. Like said above pistils will darken and trichomes will get cloudy then if allowed go amber… cloudy = energy high… amber = couch lock high… if you have no way to magnify your trichomes you can download an app on your phone I have one called “cozy magnifier and microscope” it’s not great but you can see and photograph the trichomes… here’s a couple pics that could be helpful. Your girls are definitely pretty good work… good luck
The factors that made me think this is ready for harvest are (not pictured) leaves starting to yellow and die, and plant does not seem to be taking on water any longer.