Purpling of fan leaves

You are definitely doing it right—that plant looks incredible, heavily frosted, and completely healthy! At week 7 of flower, an entire fan leaf turning purple/dark is almost certainly a natural genetic fade (senescence) combined with cooler night temperatures settling in as the plant redirects all its remaining energy into bulking up those gorgeous buds. OG Kush lines frequently throw stunning autumn colors near the end of their cycle. Since your night temps are around 70°F, it's not a severe cold shock lockout, but rather your plant naturally breaking down chlorophyll to reveal the underlying anthocyanin pigments. It is completely normal for this fading process to speed up and spread to a few more fan leaves as harvest window approaches. How to verify: * Check the trichomes: Use a jeweler's loupe or microscope on the calyxes (not sugar leaves) to check maturity. If the trichomes are mostly cloudy with a few ambers, your fade is right on schedule. * Inspect leaf stems and texture: Notice how the purple fade looks smooth and uniform across the whole leaf rather than showing speckled spots, necrotic blotches, or crispy tips? That confirms it's a natural fade, not a mobile nutrient deficiency like phosphorus.