got a 30-60x magnification of some sort?
Start checking trichomes. there are 1000 and 1 opinions on when to harvest based on color of the stalks with a bulbous head -- trichomes. As they fog up, they are near max potency, when they turn amber, THC is degrading. Some % of amber is recommended. More amber should be a more tired effect from the buzz.
i'm still working out where/when i prefer to harvest... personal preferences and a ton of time between harvests makes this a long process for anyone.