Slight discoloration on margin of leaves

emrldthumb

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I've never seen this kind of thing before, but I've only grown organically in soil before, and these are GH nutes in a DWC, so not sure if this is some deficiency that wouldn't often happen in soil. The plants in question seem otherwise healthy. Anyone have any thoughts about what might be causing it?





It's on two different plants, different strains in different reservoirs. The pH drifted a bit too high while I was on vacation a couple weeks ago, but it's been pretty stable in the 5.5-6 range since I got back. Ppm is around 450 now, res temps range from 65 to 72 (mostly lower end of that), air temps are similar and humidity is a little low (30-40% mostly, sometimes a bit lower). Haven't noticed anything like this with the soil plants in this room before or in the flowering room.

Here's a wider view of one of the affected plants (the larger one, not the runt):

 

zem

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i'd place high stakes on Mg deficiency. you can simply raise your ppm because 450 is a bit low for plants that size. you can also bring some magnesium sulfate (epsom salt) as Mg supplement but i wouldn't do that with this low a ppm
 

emrldthumb

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Thanks! Next res change is tonight so I'll increase the dose of fooood.
 

Hushpuppy

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Yeah those plants can handle about 600ppm without any issues but I would also recommend that you get a calmag additive. GH has a calmag additive I believe and it is formulated to go with their products. In hydroponics, magnesium deficiency is a commonly occurring problem.

The reason for this many people don't realize. It is because calcium and magnesium are (for lack of a better term) "bulkier" elements that will bind up with the other nutrients in the solutions and that will cause those bound elements to precipitate out of the solution and be useless to the plant. So the manufacturers only put trace amounts of those elements in their nutrient formulas.

In soil, it is not as much of an issue most often because many of the dry amendments to soil have the ability to hold higher amounts of calcium and magnesium without them being locked up. Also with soil grows that are organic, the microbes are able to unbind the elements and take them to the plants.
 
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I usually do not find that I need to add cal-mag during vegging, but you may have to. Are you using RO or bottled water?

I also think that you could up your ppms to at least 600 and maybe higher, but work up slowly when you do. I personally think some pH drift is good.
 

emrldthumb

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Interesting about why calmag matters more for hydro. I'm actually issuing tap water (bubbled and pHed 24 hours first). So the actual ppm of the solution was over 550, I was subtracting the 110 ppm that it is out of the tap to get the 450 number.

The water utility publishes water analysis reports annually, and the most recent says my tap averaged 30 ppm calcium and 8 ppm magnesium. However, the calcium range for the year was 14.7 to 56.3 ppm, magnesium was 4.3 ppm to 13.1 ppm, so it seems like those numbers are only so reliable for any given date.

I'll look into adding cal-mag. Thanks again!
 
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