Sorry, but your plant still has 3-4 weeks of maturing to do.
Lower buds = less light intensity = slower maturation.
Not sure why you are only at 40%, I would think 60-70% even at 30cm would ensure much better growth.
When flushing, just give plain water, nothing else, for the last 7-10 days before the estimated harvest date, or once approx 90% of the pistils have turned brown.
Unless temps are an issue, going up to 60-70% light intensity will also increase trichome production and quality no end over only having your light at 40% intensity.
Hope this helps,..........
Organoman.