Dark greyish green spots on leaves?


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Jul 5, 2017
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Lemon haze, blue cheese
Hi I have 4 Lemon OG haze all been doing good until 4 days ago. They started going yellow from the bottom of the plant, they were due a feed the next day so I left them. The next day I go to feed them and these spots have appeared. My first thoughts "it's a cal-mag issue" so being later in the grow I decided to give them a flush and retreat the media.
(11l pots, 50% coco coir 50% biobizz allmix)
(Canna aqua Flores, canna cal-mag agent, pk13/14, canna boost accelerator)
I flushed the media with 15l of plain water and let it drain for a while. I then mixed up nutrients, my tap water has an EC of less than EC 0.1 with the essentials EC meter. So cal-mag went in first bringing the EC to 0.2 but the cal-mag has high nitrogen so I added the same amount of PK13/14 and brought the EC to 0.4. I then added aqua flores A+B until the EC hit 0.9 PPM 630 ph5.5. Watered the plants and put them back after trimming the dead and damaged leaves off.
The problem is coming back again I think. I could just be paranoid and I've just missed them but it seems a lot to miss.

Does anyone know exactly what the problem is? Had it before?

Here's a pic I'll post more when I can thank you.


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It's sertainly getting worse on this plant. Please has anyone got a clue to what has gone wrong.


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:toke:-- looks like P defc. hitting pretty hard,... trimming the affected leaves will make matters worse, as they are sources of store nutrients, which is what causes the symptoms to appear on leaves,... N, P K are mobile within the plant meaning they can be removed from older leaves and moved to newer growth/ buds where they are needed more... the nute's look OK, especially the high PK used,... but a severe defc. is slow to correct, and the missing leaves delay that further,... another thing to check to be sure this is a simple lack-of issue, is the pH of your medium,... if it's off enough, it will cause certain nute elements to lockout and become unavailable,... adding more nutrients to off-pH soil will make matters worse as well- :doh:... the best way to do this is with a soil pH probe, like the Accurate 8 (Control Wizard), otherwise, it's the dubious run-off test,... we have an improved protocol here in this section above here,... but it's a pain to do,.. straight run-off isn't accurate at all, but it can at least offer a clue if things are badly off, so test some run-off collected in a clean saucer or somethings,.. also check EC,.. meantime, things may worsen sadly, unti things stabilize... badly hammered leaves will croak out anyway,... halting of progression is what you're looking for here!
I'm not a fan of blending coco with other soils in large amounts,.. coco is very different in it's nutrient needs and ion exchange, CEC specifically, and can make for problems when trying to deal with these type of issues,.. Coco is a Ca hog, and needs extra amounts; it can't be flushed like other mediums, or it will totally screw up the CEC (cation exchange capacity) buffering (not pH mind you, but the binding/release of Ca and to a lesser degree, Mg).... peat isn't like this,... best to go with either, not a hybrid blend until you have it dialed in,....
What kind of lights are you running? If LED that might make the cal-mag potentiation worse -happened with me up'd cal-mag (GO cal-mag) and K mid flower (increased terpinator) which helped
I'm using hps duel spectrum.
Very nice info waira. I've decided to use coco only from now on. So far I have definitely helped the situation, I flushed them twice with tap water ph 6.5 no nutrients. I've stopped removing leaves as well. The problem is slowing down and not spreading as much, raising the ph has helped but I think they are hungry now, they will be fed tonight but I'm keeping it simple this watering only adding Flores A+B ph6.5 EC 0.8
:cheers:... coco is a great medium, but solid homework needs to done on it before one dives in! it's properties lend it to making monsters in relatively small pots (most of the best growers I know of don't use anything bigger than 3gal, most smaller),... if you're up for the high maintenance! Oh, for flushing, the recommendation I got was to do this: RO/Di water, with 150ppm Ca-Mg (low N type, so watch that N%), 150ppm of appropriate nutes, pH to 6.0,... flush until run-off is at or near what's going in for ppm/pH,... this preserves the Ca/CEC buffering effect while purging excess nute salts, etc.... :thumbsup:
My only addition to @Waira 's comment would be to consider using a microsupplement when flushing with basically RO water, even though it's considered trace things like zinc etc. are not found in a lot of nutrients. Speaking from experience, I've flushed and ended up giving the girls micro deficiencies (some of which can look like early signs of the initial problem) which can easily spiral out of control. Earth juice microblast is good stuff. Also, a little K (especially in flowering when you can just bump it up) can go a long way to correcting a Ca def in coco as K in sol'n will help buffer the leaching of Ca which is usually 1:2 Ca:K in coco (think equilibrium, concentration as well as charge gradients etc.) if that makes any sense -cheers!