Well i'm not an expert but judging by your pictures (expecially judging from the yellow leaves but also from the appearance of the buds) i would definitely harvest. If alle the leaves are yellow there is no point in keeping her under the light. However, the best way to determine if a plant is ready to harvest is to look at the trichomes as the other guy said. If they are all amber i suggest you to harvest NOW because THC is converting into CBN, which is not necessarily a bad thing, it always depends on what you want; the harvest window range is pretty wide and i personally harvest when about 50% of trichomes are cloudy and 50% are amber.
Also, your buds look astonishing, i don't know how you resisted harvesting until now, really amazing.😋