Curly leaves and brown spots

here is my problem:

A couple of my leaves edges are curling up with brown spots.

I have:

77 F on average
Ph 7,5
Moisture 60 %
No visible pests

Edges are slightly dry but leaves are not crispy but drier than a few days ago

A few days ago my dehumidifier conked out and spiked at 86, with humidity down to about 45-50. for about 4 hours

VPN chart says I should up the moisture...

Using organic soil which had a slight nute content; transplanted 2 weeks ago into said soil. No nutes added.

Mag/cal deficiency?

Need to act fast, as plant still fairly Young

Never had that problem Outdoors even though we had temps up in the low 90s for about a week...

HEPLP

Oh, and it’s in the upper leaves mainly

Looks to be deficient in potassium..

Rainbow Warrior said:

Oh, and it’s in the upper leaves mainly

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Are you using LED? If so what kind and how close is it?

hotrodharley said:

Are you using LED? If so what kind and how close is it?

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400w hps; the light is about 18“ above top of plant

Rainbow Warrior said:

400w hps; the light is about 18“ above top of plant

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Personally I would raise it unless it’s in an air cooled reflector. I see heat stress.

Heat stress and what I call light over saturation will exploit any deficiencies that may be apparent

Lower your ph and your problem will fix itself. Magnesium can hardly be absorbed at 7.5 and it's messing with your other nutes. If your ventilation is good and you don't think it's too hot, I can almost promise you it's your ph. Water with 5.5 or 6 to bring it down, add a touch of 3% peroxide if you're close to overwatering.

Ph is 7.5?

There is one problem.

Yep ph IS the issue

Aqua Man said:

Yep ph IS the issue

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I read that u can use lemons or vinegar to bring down ph, trying to stay away from chemical adjusters.

Rainbow Warrior said:

I read that u can use lemons or vinegar to bring down ph, trying to stay away from chemical adjusters.

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You can. I'm not a dirt guy i grow in hydro so I would not. Vinegar and lemon juice are not near as stable and break down easier.

THB in soil you want to create a mix of soil that will buffer your PH so you don't have to. If you want to go natural peat moss will lower PH. Like i say i'm a hydro grower so I would ask the soil guys what your best options are. A pH of about 7 in soil should do you well.

As far as your VPD those charts can be deceiving. Since in order to truly calculate it you need the leaf temp included. Take a read here, it will help you get a better understanding.

https://www.questclimate.com/vapor-pressure-deficit-indoor-growing-part-1-vpd/
https://www.questclimate.com/vapor-pressure-deficit-indoor-growing-part-2-vpd-important/
https://www.questclimate.com/vapor-pressure-deficit-indoor-growing-part-3-different-stages-vpd/