Halloweed said:

Hello fellow growers.

I've got an auto growing in an earthbox, buildasoil 3.0. Temp around 75°f, rh 60%.
Water Ph 7.0 approx. Tap comes out at close to 9.0.

Ppfd of 650ish at the tops about 10" away. She was nitrogen toxicity I think but starting to notice brown splotches on some leaves. I'm also seeing purpling of stems an at the bottom of the plant leaves are getting a light green.

Does this seem to be a deficiency or something worse?

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Ninjadogma said:

If you're looking at tap coming out at 9, I would be very suspicious of the pH pen's accuracy. EPA recommends a range of 6.5-8.5 and most municipalities set an internal standard between 7.2-7.6.

So just as a thought exercise and that's all this is intended as, let's suppose it was really 7.4. That would mean your pen was about 1.5 points off. So when you adjusted to 7.0 you really adjusted to 5.5, which is way to low for calcium uptake, and now we wee calcium deficiency showing up as brown spots on the leaves. Plant is also going to begin losing phosphorus so you'll see some colors like red and purple showing up on stems and leaves. This happens when it's cold but when it's not cold, it's missing phosphorus. At that lower pH we also begin to lose potassium, and since we aren't seeing that, just consider it a thought exercise and you probably just have a hungry plant. But I would check that your pen is calibrated right and test it independently with a sample you are absolutely sure of it's pH value to compare against what the pen says. I have a swimming pool so I have red phenol drops. I check a color reading with the drops and then I check what my pen says.

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Halloweed said:

That was explained very well, thank you. I'll check my pen when I get home. Got it a few months ago, ac infinity.

I'll add some buildabloom and buildaflower. I have Cal Mag but then I guess I couldn't call it organic. I'll see what else I can use that is but it doesn't matter as long as she's healthy.

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