Brown/Rusty spots on leaves after dark period

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THraCian

THraCian

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I spotted some brown/rusty spots on some of my plants leaves after their dark period. Before lights out I didn't spot any of them, humidity was up quite a lot about 70%, because it's raining and I still don't have a dehumidifier, but not sure if that's the issue. They are 22 days old (since seed in ground), about 15 days from sprout. I am using BioTabs Just add water strategy using tap water that stayed outside for a few days and BioBizz LightMix with some Perlite added for medium. I only water once the top 3cm(about an inch) of the soil is dry.

From my research it looks like a Calcium deficiency, but this is my first grow ever and I am not experienced enough to recognise it correctly.

Any ideas what might cause this?
 
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mysticepipedon

mysticepipedon

2,780
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LEDs? you might have to turn them down a little.

I'm new to LEDs, so I could be wrong about anything I'm saying here, but check to see if the brown spots are only on the parts of the leaf that gets hit with direct light. Do the parts shaded by upper leaves have brown spots too?

My hare-brained theory is that if there is a Mg deficiency and the plant draws a little Mg from lower leaves, those leaves burn between the veins.

But always keep in mind that I may be way off base. You might be watering improperly.
 
THraCian

THraCian

5
1
LEDs? you might have to turn them down a little.

I'm new to LEDs, so I could be wrong about anything I'm saying here, but check to see if the brown spots are only on the parts of the leaf that gets hit with direct light. Do the parts shaded by upper leaves have brown spots too?

My hare-brained theory is that if there is a Mg deficiency and the plant draws a little Mg from lower leaves, those leaves burn between the veins.

But always keep in mind that I may be way off base. You might be watering improperly.
Yes, I am using LEDs, Mars Hydro TS1000, it's about 50cm(20in) away from the top at 75% intensity, but the top leaves don't show any signs of those spots, and one of the leaves with the spots is actually shaded by another leaf.
 
mysticepipedon

mysticepipedon

2,780
263
Yes, I am using LEDs, Mars Hydro TS1000, it's about 50cm(20in) away from the top at 75% intensity, but the top leaves don't show any signs of those spots, and one of the leaves with the spots is actually shaded by another leaf.
I think the upper leaves have better nutrition, because they can take nutrients from the lower ones, and that stops them from burning (All part of my theory, which may be total bullshit, but I'm going with it for now).

Check to see if the shaded parts of the lower leaves are suffering, or if it's only the parts of the leaves exposed to direct light. That's what's happening in my tent.
 
THraCian

THraCian

5
1
I think the upper leaves have better nutrition, because they can take nutrients from the lower ones, and that stops them from burning (All part of my theory, which may be total bullshit, but I'm going with it for now).

Check to see if the shaded parts of the lower leaves are suffering, or if it's only the parts of the leaves exposed to direct light. That's what's happening in my tent.
It seems even the shaded parts are affected, but only on a few leaves of the entire plant, not every leaf. Also today they started wilting.
 
THraCian

THraCian

5
1
Update: All fine now

Ordered BioBizz Calmag + Leaf-Coat and noticed bottom of pots were wet.

Oct 15 - While waiting for the Calmag and Leaf Coat, I thought about the root zone and lifted the pots to check the bottom and surprise - they were wet. It seemed that the water was going down, but there were drops of water on the bottom of the tray, so the soil was always wet there. I went to the hardware store and picked up coasters for hot pots and pans ( it's basically like a lifted grill 1cm above the ground ) with the idea that the air from the fan will dry out the bottom of the pot and won't cause this to happen again. I added 400ml of water to each plant with CalMag and sprayed them with Leaf Coat.

Oct 16 - The plants basically recovered overnight and were as healthy as ever. Not sure if it was the Calmag, the leafcoat or the coasters to try out the bottom of the pots, but my best guess is the coasters that lifted the pots, because the bottom wasn't dry anymore. Also got an TDS meter, and my tap water after aerating and leaving out for a few days was about 250-280 ppm, so cal shouldn't be an issue.
 

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