@Indy73 lots of helpful people on these forums but also a lot who like to make others feel small. Not sure what their insecurities are but that's the internet for you I guess.
Anyway, the tip Wet Socks gave you about a mini microscope/jewelers loupe is correct, below is a link that sells both together...
Most people like to harvest when the trichomes are still transparent but some are already cloudy, before they start to turn amber (amber is when they are starting to decompose and THC content starts to diminish). You will need one of these mini microscopes to see this...
If you don't want to go this route, here is a paragraph on harvesting out of Jorge Cervantes' Indoor Marijuana Horticulture book:
"Diminishing returns in the point reached when the hair-like pistils on the bottom of the bud are dying (turning brown) at a faster rate than they are growing from the top of the bud. At this point, THC production has usually peaked out and is on it's way down hill. This technique is the best way to tell a ripe bud with the naked eye."
As for flushing, Jorge also says:
"Stop fertilization one or two weeks prior to harvest. Latent nutrient accumulation in foliage imparts a fertilizer-like taste. Leach nutrients from the growing medium a week before harvest."
I follow his advice and have always had excellent crops. I'm growing organically this time with gaia green so I won't be able to stop fertilizing a week or two before harvest as it's already mixed into the soil. I can only hope that most is used up after the 4 weeks since the last top dressing of the power bloom.
Best of luck. Your plants look great.
KINGMAS Mini 60x Microscope Magnifying with LED UV Light Pocket Jewelry Magnifier Jeweler Loupe with 10X Folding Pocket Magnifier : Amazon.ca: Toys & Games
www.amazon.ca