Pics 2, 3 and 4 show amber trichomes, personally I would be harvesting now/very soon.
Harvest when you have 90-95% brown pistils for a THC influenced mind bending head high.
Harvest when you have 98-100% brown pistils for a CBD influenced, heavier and sleepier body stone.
Let you preferred type of effect guide your harvest timing.
Personally, I prefer pot that gets me high, not puts me to sleep and this is why I would be harvesting asap.
Flush by giving just plain water for the next 3-7 days, this will be adequate. There is no need to drown your plant, just give an ordinary amount of plain water nothing else, the same amount and frequency as you would normally give each irrigation, the idea is to remove nutrient salts from the plants' cells, not to leach the bejeezus out of the substrate. If you prefer late picked CBD influenced flowers, extending the "flush" to 7-14 days can also be done, but for all practical purposes, three irrigations with plain water over 5-10 days is sufficient in my experience, however I really cut back on the nutrients as harvest approaches, not stop them all together, just reduce them to a half to one third the amount in the last 3 weeks before harvest and pre "flush".
For those playing along at home............. and are aware of my ramblings..........
This question illustrates quite nicely why I advocate the "pistil colour/condition" method over the "trichome colour" method, - as can be seen, this plant is well matured, yet only showing a very few amber trichomes, which is genetically linked and it is not necessarily a "state of maturity" link.
Waiting for this plant to achieve the magical so called 30% amber trichomes as the sole deciding factor as to when to harvest, would potentially lead to this person harvesting a near dead plant with vastly degraded trichome chemistry, producing a no doubt, B grade effect.
Pistil colour/condition is directly linked to plant health, and it is plant health that determines trichome chemical composition, whereas trichome colour on its own does not affect trichome chemical composition.
Hope this helps, Organoman.