Blackening of Leaf mid-Flower

I'm running into an issue with this one particular White Widow from Crop King. She's a little shorter than the other two from the set of seeds she came from but I've rarely seen bud development like this so I want to make sure I'm not doing something stupid to cause this.

Strain: White Widow (Autoflower) from Crop King Seeds.
Week: 6 of flower (approx.)

I noted some pH related issues such as immobile deficiencies and went ahead to check the runoff pH which went from 7.0 in to a runoff of 5.4, telling me somehow my pH went wonky. I flushed to a runoff pH of 6.5 then fed 1/4 strength nutrients (FF Cultivation Nation) a lot of the spotting has subsided but now I've got these kolas covered in dark leaves. Please help me figure out what's going on.

The small plant is the one with the issue.

She’s just maturing probably. Could be P deficiency or cool temperatures too though.

Merlin1147 said:

She’s just maturing probably. Could be P deficiency or cool temperatures too though.

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My Temps are between 66 and 74F, plenty of phosphorus and potassium. I was thinking the same thing as you but the trichomes don't really seem to agree. None are cloudy that I can see. It also seems to have worsened after the flush.

Whatcha think?

Forgot the trichome photos

I little cool. Can you bump the temp to 78-80? P uptake is sensitive to temp.

Merlin1147 said:

I little cool. Can you bump the temp to 78-80? P uptake is sensitive to temp.

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I've found that this White Widow strain actually likes cool temps around 65 to 75 through previous runs. It doesn't react well to temps above 75F, because of how the humidity where I live works. From what I have been able to gather through a few personal professional growers is that it may be a striking excess of phosphorus though I kind of doubt it given that I had flushed to correct pH to 6.5 (from 5.4!!!!) previously, removing ALL salt build-up. After that it got /worse/. First photo is from two days ago, second photo is today.

Looks like she was just maturing. The same thing appeared on my other two as they reached the same week.

And she's done. Putting her into 48hrs of darkness then off to chopping. Thanks, mate.

Tech_and_smoke said:

Looks like she was just maturing. The same thing appeared on my other two as they reached the same week.

View attachment 4708369

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What was your take on how close he was? I have a very similar plant that I assume is P deficient. I’m 16 days from the short end of expected flowering time for these strains.

The unfortunate thing is, I've got a plant doing that right now. It seems like she's a week or two behind the others but is starting to turn.

Really you just have to keep an eye on trichome color and cloudiness. Majority milky/cloudy, you're only a couple days out in my experience.

Oh my god, I just posted a question about this and mine looks just like that

North... said:

Oh my god, I just posted a question about this and mine looks just like that

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No way

Cool night temps and strain will cause the purpling of the leaves.