I plan to reduce red light, increase blue, and int...

The cloudiness of the trichomes is what your looking for to tell you when it's time to harvest..to dark amber you couch locked to clear a headache .use a jewelers loupe mine is 100x with a light and it works but does strain the eyes ...my soil grow I did a 1week flush with florakleen and she was good smoke grey ash... I also put ice cubes and colder water in the plant pot for the last two days to try and cause shock to produce more resin good luck with the girls ...

the only reliable way is to monitor your trichomes with a 30x or better 60x magnifying glass. You want to harvest with the highest percentage of cloudy milky trichomes as possible. Clear trichs=not ready. cloudy=reaching maximum thc level. amber= too late your thc is converting to cbd and other less desirable compounds. I start flushing when I get about 10% amber and they are usually good for me in about a week. You will get different effects depending on when you harvest. A early harvest with several clear trichs will give you more of an entergetic high where a late harvest with a lot of amber will give you more of a sedative couchlock effect. It is really something you have to experiment with to see what you like. In your situation you want to flush the soil for about 2 weeks anyway. I would start your flush at about 10% amber and switch your lighting at the same time you start your flush. You have a little window of time from really ripe to overripe so that should put you at a good harvest. Hope this gets you headed in the right direction.