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Magnesium? Iron? Deficiency or Toxicity?

A

accid

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Hey all,

I posted this on "Sick Plants" but after 38 views and no responses, I was hoping someone who has had this issue before could help me out before its too late. Sorry Mods~! Hope you can understand this one and I also included good photos in the event that others run into this same issue.

I am well aware that magnesium deficiency causes yellowing and rust spots, however the issue I am having is that the leaf tips are all curling up and inward. You can clearly see this on these photos. From my research it leans toward magnesium toxicity however there is very little information in regards to toxicity but abundant in deficiency. Im guessing some of you have had this experience but I do not want to be led astray.

The reason I believe that it is not magnesium deficiency is that there are no rust spots. This is grown in coco (Just Right Xtra), my ph levels are fine at 6.0. I was thinking heat stress but the heat peaks at 80 degrees and 66 at during dark hours. Humidity at 40%.

I would highly appreciate some help. Thanks a bunch!

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k0rps

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:yeahthat:

From the curling of the leaves, it looks like heat stress. Could be from the light being too close.. How far is your light from the tops?
 

Hushpuppy

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I am inclined to believe that to be a heat stress issue as well OR maybe overdrying from dry air being blown onto the plants with fans. The yellowing looks like late flower yellowing.

However; given that you are in coco, there is an issue with coco where magnesium gets locked up a bit by the coco, it has something to do with cations and calcium in the coco. Basically you need to suppliment with extra cal/mag throughout the grow in coco, and the more coco the plants are in the more pronounced this can be. I am attaching some infor from a copy of "Marijuana Garden Saver" that tells the same symptoms that you have. I can't swear that this is the case here as I don't know if you are supplimenting with cal/mag(or supplimenting enough). Hope it helps though :)

View attachment magdef clip.bmp
 

Hushpuppy

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The clip above was manipulated in MS Paint so it should open automatically if you have MS Windows :) If it doesn't You may have to download it and open with your Paint program manually
 
A

accid

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The plants are 11-12 inches from the bulbs (400watt). I have no direct air blowing on them (yes i am well aware of the repercussions on this not developing a strong stalk). I give them 5ml of calmag per gallon of water. I give them calmag every watering. I have been using coco for two years now and it is absolutely essential that they have calmag with every watering.

Hushpuppy, I read that same statement in a book. What's interesting is that magnesium deficiencies are rather noticeable with the rust spots. I was curious if this could be magnesium toxicity but it is difficult to find images of it on the net and books do not touch on mag toxicity cause of its rarity.

I have three strains atm. This is only affecting the strawberry blue strain. The others are perfectly fine. Through my reading I think its either heat stress, iron deficiency or some type of magnesium issue. When reading other forums people say the leaves are "praying for magnesium" but it doesn't have the symptoms of mag def. Anyhow, I was hoping has seen this before and figured it out. I'm sure this has been an issue for someone or will be for someone at some point and it would be great if we could figure this out. Thanks all for taking the time to share your input. Any other suggestions would be great.
 

Hushpuppy

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You said that you don't have any fans in the space? Maybe that is just enough for this particular strain to begin to stress a bit. It certainly wouldn't hurt to put a fan blowing across the tops of the plants to cool them just a bit. I try to keep my air moving as much as possible without blowing leaves too much but to keep the air stirred up good.
 

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