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Thread: Dark spots on leaves leading to yellow/necrotising leaves - HELP!

  1. #1

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    Default Dark spots on leaves leading to yellow/necrotising leaves - HELP!

    Hi guys,

    This is my first grow; I've made lots of rookie errors along the way but have managed to make to Week 8 relatively unscathed until now...

    I've got two 12L pots growing outdoors. First one an "Alpujarrena" seems OK, but it's started getting yellow leaves towards the bottom of the plant.

    The second, BCN Critical XXL, has been slightly more temperamental. It had a short bout of powdery mildew that I think is now under control, but over this past week it developed small, dark brown dots on the leaves; and now those leaves are turning yellow/completely necrotising all over the plant.

    Photos attached. Three close-ups are the BCN, the other is the healthier Aplujarrena.

    I know I'm in a hard water area and this is the info I've managed to get from my supplier:

    Calcium carbonate(CaCO3): 280 ppm
    Degrees Clarke:20
    Degrees German(DH):16
    Degrees French:28

    I bought an admittedly cheap ph probe, and it seems like my soil (and water supply?) is running too alkaline, fluctuating between ph7 - ph8.

    If it's always been that high, I'm confused as to how I managed to get by this far without having issues?? I've got other bits and pieces like veggies and ornamentals, growing fine, but I guess they don't mind higher ph's.

    Finally in terms of feed...I made the rookie error of growing both plants in Miracle Gro All Purpose Compost. It's meant to have 6 months worth of slow-release nutrients (annoyingly I don't it doesn't tell your the NPK breakdown) in there so up until now, I haven't fed them with anything else. During the early stages, I definitely noticed some nutrient burn but the week before this all kicked off, everything seems pretty green and healthy.

    I've now bought some BioBizz Bloom - and have done two doses this week, along with a small dose of Epsom Salts just in case I've got a Cal/Mag issue.

    Any advice hugely appreciated - I'm gutted to have come this far and now things look so bleak!

    Shout if you need more images of the bud(lets) etc (they seem fine enough, maybe a bit on the small side).

    Click image for larger version. 

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  3. #2

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    Are you getting good runoff every time you water? While your water is hard it's not too hard to grow decent weed in.



    J

    "If science can't be questioned, It's not science anymore"

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    Thanks for the response man.

    Yeah both pots seem to be draining/running off pretty well with every watering.

    Just can't think what's suddenly caused such a drastic turn for the worse...We had a lot of rain/storms last weekend, but the small dark spots had already started to appear by then.

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    Quote Originally Posted by D1LDN View Post
    Thanks for the response man.

    Yeah both pots seem to be draining/running off pretty well with every watering.

    Just can't think what's suddenly caused such a drastic turn for the worse...We had a lot of rain/storms last weekend, but the small dark spots had already started to appear by then.
    I would get a good cannabis feed and feed the basic nutrients, might add in a little bit of calcium and magnesium. I think your plants will come around after that.



    J


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    Appreciate the calm advice! I've bought some BioBizz Bloom if you're familiar with that? Would you also recommend a grow focused feed too? I know BioBizz have a "Grow" feed too that you can combine with the Bloom.

    Big thanks,

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    Quote Originally Posted by D1LDN View Post
    Appreciate the calm advice! I've bought some BioBizz Bloom if you're familiar with that? Would you also recommend a grow focused feed too? I know BioBizz have a "Grow" feed too that you can combine with the Bloom.

    Big thanks,
    You would probably be better with a grow focused feed for about another month and then switching to Bloom would work okay. I think the bloom nutrients wouldn't have quite the nitrogen you want and would have a little bit more PK than you really need. I don't know the exact mix of that biobiz, but it may be a little bit lacking in some of the micronutrients you get in a grow mix.

    Hopefully my memory is correct when I'm thinking you're doing an outdoor photo period strain.



    J


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    Ah so I'm actually working with autoflowers (just noticed I hadn't mentioned that above, apologies).

    Does that change your thinking? I've just entered Week 9; buds pretty small still on both plants.

    Do you reckon that the Miracle Gro compost will have used up all it's pre-feed nutrients by now?

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    I think that Miracle-Gro probably is getting close to being used up, I would just feed those bloom nutrients kind of weak at first with every watering just to see how it responds you can adjust after three to five waterings.



    J


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    This is pretty much the exact same issue Ive been having with my grows for the past 2 years! Have tried pretty much everything and im still dumbfounded. What makes this interesting for me is that it is an outdoor grow while mine have all been inside so i can at least rule out that it's not a LED problem. Good luck fella!

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    Thanks man - I'll keep you posted with an update a little later this week. Would you bother with Epsom Salts at this stage?

    @Kurdt - that's sort of reassuring to know! Have you still managed to harvest a reasonable amount?

    It's a real mystery, the other plant seems to be OK other than a few yellow leaves towards the bottom..But the BCN has been decimated. Wondered if it could be leaf septoria but would imagine they'd both get then.

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