Strange Leaf Blight - Grey Blotches

[Tilopa]

I have some sort of plant disease I believe. My leaves show blotches that progressively get worse - pics attached. I have researched from good and thorough sources and cannot find the cause of this particular leaf symptom. The leaves start off with only a few blotches (which are kind of a greyish color and get worse covering most of the outer parts of the leaf before it dies and dries up. Strangely the disease effects only the lower half of the plant, which made me think of root disease but I looked into the possibility of Pythium thoroughly and I'm sure it is not that. What other root diseases could cause this type of leaf symptom?
I have sprayed with Neem oil and it has no effect.

My setup is as follows:
Flood and drain system with a 100 gallon res and 4 x 8 tray. Medium is coco coir in 3 gallon "smart pots". I water twice a day during light cycle only of course. There is plenty of fan movement in the room and temp usually stays between 72 and 78 but sometime goes to as high as 84. RH is usually around 45 but has climbed to as high as 60.

This problem is definitely affecting yield. I am desperate to figure this out so any help will be greatly appreciated.

 

[The Butcher]

have you checked your PH yet? Thats the most important detail of all. If your PH is to acidic then you would have the effect you are having right now. Ph is the lifelin to your plant, be sure to keep it within range. Let us know when you can

 

[Tilopa]

Thanks for the reply.

I check my PH about every other day, and it always tends to rise. Usually when I check it it's about 6.2 to 6.4 and I then bring it back down to about 5.8. It is rarely ever below 5.8 and usually a bit on the high (non-acidic) side.

 

[The Butcher]

whats the nutrient regimen like? high ppm/EC ? what type of nutrients are you using and whats the age of the plants. It can be nutrient burn if your running to high of a ppm/EC count. Dunno just yet, feed us the info as you can. I'm going to stick this one out with you till we can get some sort of consensus of what it may be.

Take a look at this and see if theres anything that you may be able to pin point as a problem. Here you go:

Cannabis Plant and Pest Problem Solver - Pictorial

 

[Wingman420]

It does not look light nute burn as this usually occurs at the tip of plants. Butcher is among our finest connoisseur's of all things green. Let us know whats up and keep us posted.
+Rep
Also check out the link in my signature to post pics directly into thread.

 

[SnowBender]

Vegging? looks like a P def.

How much water is left in the rez when table is full? My friends all use 250-300 gallon rez for 4x8 coco.

Along with nute regime, whats is your flush routine?

Whats the EC/ppm doing when the PH goes up?

 

[Tilopa]

Sorry for the delay in responding and thanks for all the replies.

More details about my setup:

100 gal reservoir that I change every 7 days. Nutes are Cutting Edge Solutions base, plus Uncle John's blend, plus hygrozyme, plus just starting using Bloombastic.

Plants are about 3 weeks in Flower, starting seeing the symptoms at about 2 weeks. These were vegged in a separate room with separate res for about 4 weeks, no symptoms in veg.

I'm not up on the EC stuff but I check my ppm after I change the res weekly and it is about 1500 ppm, by the time I change the res it is at around 1100 ppm. ppm must be going down as the ph is going up.

Someone told me that they thought the leaf issue was from wind burn, they had the same issue from fans being too close and high on the leaves. I did a search for wind burn leaves photos and the photos looked very close to what mine look like. This seems unbelievable to me that this could be it. I do have fans at each end of the table and hitting pretty hard at those ends, but some of the leaves that have the symptoms are in the middle of the table where I would not expect THAT much wind.

Does this seem like a plausible cause to you?

 

[cflgrower]

man i sure am glad i read this thread...im having the same problem...and off the back i thought the fan,but figured i was completely wrong.....my leaves looked just like that...and i have a huge oscillating fan on the side that received the damage....fixing my ppm level also helped my leaf tips....

 

[hbenz]

hey guys dont know how to do the qoute thing but i am having the exact same problem, leaves look the same, i am 18 days into flower and problems seem to be mainly on plants closest to fans but stil shows on other plants.