K deficiency?

Hello all, I have a small issue going on I have been having troubles with diagnosing. I just came back from Vacation for 8 days, and came home to changes in the tent. The plants look overall great, however there are leaf edges on a few plants that have gone yellow or have yellow spots on the upper leaves. The tips don’t seem burnt apart from a couple of the affected leaves.

-200W MH fixture - 24” above canopy
-2 month old plants from seed.
-Water with Deer Park bottled water, once every 6-7 days
-Exhaust fan, a fan for the canopy and tent itself along with a fan for the lower leaves
-Temps range from 70-76F
-Happy Frog soil, 1/3 perlite
-Not adding nutes yet, as I figured the soil would still have some to offer
-1 Gallon pots, well drained and last repotted 4 weeks ago.

I was thinking K deficiency from the research I have done. I’m not sure if it is nute burn, as the problem is quite recent. I had also potted these 4 weeks ago into the new Happy Frog Soil. I would think nute burn would have acted sooner? Plus apart from a couple leaves, the leaftips appear healthy.

Thanks in advance, It is my second grow. I do read as much as time permits me to, and have before I started this venture. So I have a decent understanding of the plant chemistry but apparently need to learn more.
 
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-Not adding nutes yet, as I figured the soil would still have some to offer
I would feed one and see what happens. My guess is they're hungry. But, you could limit the risk by feeding just one.

If it's k-def, and you haven't been feeding... maybe the k is depleting first. But, that probably means it's close to everything being depleted.
 
I can try that. I’ll see what feeding one at this time will do for it. If I get positive results I’ll continue with the others.
Thanks for the advice!
 
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With Fox Farms stuff, the last thing I would expect is a deficiency, although a lockout situation is much more probable and shows the same symptoms if there is too much P in the soil, which interferes with the K uptake (and vice versa, I think) I would check your Ph and PPMs to rule out Ph issues or overfeeding. Some plants just don't seem to do well with FFarms stuff, I don't know why but Indica seems to be more affected.
If you aren't watering much, the low water amounts in the soil allow the nutrients to be released, but they are concentrated from not using enough water to dilute them to less potent concentrations. As time goes on, the nutrient levels can creep up and cause issues that weren't there before. I would give it a good drink with a decent amount of flow-thru coming out the bottom. Concentrated nutrients are usually acidic, which can further complicate lockout issues.Ideally, I would test it for the PPM level. It sort of looks like a magnesium deficiency start, but a dose of foliar cal-mag/Epsom salts should clear that up very quickly if that is part of the problem.
 
Understood. I will check the Ph of the soil and runoff and see where it’s at. I do need a Ppm meter. So I’ll be getting that online this week.
I do have a noob question pertaining to foliar feeding as I’ve never tried it before.
How does one foliar feed with Cal-Mag, or epsom salts? Idk why but I am having difficulty finding instructions for those. I do have Cal-Mag, and epsom salts, but cannot seem to find a proper dosage that
Is recommended for foliar feeding.
Thanks for the reply
 
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Iirc Happy frog is not as hot as ocean forest. I think after a month in that soil it might be depleting nutrient reserves. It absolutely looks like potassium deficiency to me.

I'd pull a slurry test and check things out but I'd also feel pretty comfortable giving them a feeding. They look hungry.
 
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If you fertilize start with a very low concentration. 15-25% of directions max. Also good to wet the soil with fresh water some first to avoid burning the roots.
 
Thank you both.
I will try feeding them a smaller % of what the bottle recommends and see if it helps. As well as wet down the soil beforehand. I agree after a month, they probably are using up a majority of certain nutrients. Definitely doing a slurry test today.
 
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Thank you both.
I will try feeding them a smaller % of what the bottle recommends and see if it helps. As well as wet down the soil beforehand. I agree after a month, they probably are using up a majority of certain nutrients. Definitely doing a slurry test today.
I agree about possibly giving a very light snack. Foliar feeding is a very simple way to feed directly, but not all nutrients can be used this way. In general, if it is all water soluble, then it is probably OK for foliar feeding. I'd recommend a 10% dose or less on a section of the plant before spraying everything down, in the event that the plant doesn't react well. You will see the benefits quickly, but if it causes problems, the damage is limited to the applied areas. You can base your treatment on the results. I have seen results overnight in some cases
 
That’s a great idea, I’ll limit it to one plant on one side, and see if it helps. I definitely need to learn how to foliar feed, so this will be a good learning curve. I’m reading to try and limit these feedings to once a week?
I have Calmag+and CNS 17 3-2-1 from Botanicare that I used from my last grow.
 
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I definitely need to learn how to foliar feed, so this will be a good learning curve.
If you foliar feed, don't do it under the grow light. The water droplets can focus the light and burn the leaves. (You don't have to worry about this yet, but: you have to be careful doing this in flower because wet buds can develop mold too. Your climate/RH can make this more or less of a risk.).
 
Thank you az2000. I was wondering that as I knew general watering can cause this. So is it best to do it while lights are out for the night?
I read some people do it, but raise the light while it is on.
I’d prefer the safest method
 
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Agreed, I like to foliar spray about half hour before the lights come on. But I do it very rarely and only for pesticide applications these days. If fed properly in the soil they shouldnt need a foliar feeding, and it just increases the risk of mildew and mold. I much prefer to keep the plants dry at all times.
 
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Thank you az2000. I was wondering that as I knew general watering can cause this. So is it best to do it while lights are out for the night?
I read some people do it, but raise the light while it is on.
I’d prefer the safest method
I take mine outside on the patio (shade, indirect light). After it dries some, I let them have direct sunlight or awhile. (I'm in the desert where the sunlight is strong. In a more temperate climate, maybe direct sunlight on wet leaves would be ok). One risk outside is that you'll pick up a pest and bring it in.
 

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