Youve gotta watch the trichomes. A digital handheld microscope works great but even a $20 jewellery loupe works. When the trich heads are clear, there isnt much there but as they get cloudy and turn milky white, this is when the vast majority of cannabinoids and terenes are developed. Once the trichs start turning amber, this is when it stops producing terpenes and where cannabinoids and terpenes start breaking down. Is it possible that the last plant you harvested was allowed to ripen enough that all the trichomes turned fully cloudy, with maybe the odd amber one here or there? Also, its possible that the plants you harvested earlier still had some nitrogen built up in the tissues and the last plant you harvested had more time to consume the extra N. I only use the hairs as an indicator, once the hairs start turning orange, its time to start watching the trichomes. I havent been following your grow so i dont know the specifics but this is what comes to mind when i read your last post.i just harvested my first grow. 5 plants, one at a time as they matured. i noticed the one that was the earliest was the most hay smelling one. the one that was the most mature had/kept the best smells. that seemed to make more difference than how or how long i dry/cured them. on all, i smoked some as soon as it was dry enough, and that one tasted better from the start, and a lot better as it cured. i had 2 of the same strain and the one that was older when chopped had the sweet taste the description said it should.
Congratulations on your harvest by the way. Its very satisfying to smoke something that you grew start to finish, something you know isnt dirty or laced or full of nutes. Enjoy it