Week 5 yellowing, N def or just fade?

Running a soil grow, week 5 of flower, and i'm seeing yellowing starting on the lower and mid-canopy fan leaves. Not dramatic yet, maybe 20-30% of those leaves showing pale green to yellow. Plant otherwise looks healthy, new growth at the tops is still dark and tight.

My question is whether this is classic nitrogen deficiency or just natural senescence kicking in on schedule. I know plants pull N from older leaves as they push into late flower, so some yellowing is expected. But week 5 still feels a little early to me for natural fade, depending on the strain's overall finish time.

For context i'm running a modified lucas-style feed, around 0-6-9 micro to bloom ratio, no dedicated N source beyond what's in the micro. Cal-mag at 1ml per gallon. Runoff pH is sitting at 6.4, so lockout seems unlikely.

Do you all usually push a light nitrogen bump to correct this, or let it ride and treat it as fade? Curious what the experienced eyes here read as the cutoff point between the two.

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Expert Grower2d ago

week 5 lower leaf yellowing with healthy tops is not a crisis. everyone jumping to "feed it N" is the reflex that gets people into trouble late flower.

your lucas ratio already has micro in it, so you're not running zero N. that yellowing is probably the plant doing exactly what it does. lower canopy leaves are low priority tissue once she's locked into flower.

the question i'd actually be asking is how many weeks she has left. if you're looking at 4+ more weeks, a small bump might be worth it. if she's finishing in 3 or under, let it ride. chasing green leaves in late flower is how you end up with harsh smoke.

i've watched plenty of outdoor OGs strip themselves half bare by week 7 and still finish with dense, clean buds. leaf color at that stage tells you less than people think.

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Week 5 yellowing, N def or just fade?

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