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Thread: Brown spots and yellow leaf tips on 2 week old plants in DWC

  1. #1

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    Default Brown spots and yellow leaf tips on 2 week old plants in DWC

    Hi fellow growers, I'm on my second attempt at cannabis in DWC (had much luck with veggies, but due to my pH meter getting un-calibrated since then, fried all but one of my first batch of cannabis plants). I'm growing feminized autoflower seeds.

    Things were going quite well up until a few days ago, almost ahead of schedule. Noticed some yellow tips on the two sets of full leaves, only the middle, largest leaves, though. Was limited to one plant, which was a few days ahead of the second, but now the second is showing the same brown/yellow tips as well as some brown/rusty spots. Pictures: postimg[.]cc/gallery/zqPGGMt

    I'm growing in 5g black buckets with 8" netpots with hydroton as a medium, airstone. Seeds started in rockwool, rockwool was pH balanced, hydroton was rinsed clean. They have been in the buckets for about a week and a half and up until 2 days ago looked healthy. Nothing changed with the nutrient solution. Using an off-brand QB with 85w draw rated for 2.5x2.5', originally was about 16" from the plants, but I moved it up to 22" when I first noticed the issue, thinking it could be light burn, as they are still young.


    The one surviving plant from my first batch recovered nicely and is not showing the same yellowing/browning and is quite happy after fixing the pH issue, and has the exact same nutrient solution, just a bit higher EC, as it's older. The two younger plants that are having issues just started to drop roots into the the res and look healthy. I did a res change last night and the older plant is looking like the yellowing tips have not spread and doesn't have signs of brown spots, but the younger one has brown splotches spreading further on the first set of leaves,


    Parameters:

    Temp: 68f (lights off) - 78f (lights on)

    Humidity: 50-65%

    Light cycle: 20/4


    Nutrient solution:

    Tap water, de-chlorinated (base EC 300uS)

    .5 tsp / gallon (half strength) general hydroponics flora 3 part (equal parts of all 3 for veg)

    .5 tsp / gallon of GH CaMag

    Half strength Orca Bacillus/Mycorrhizal inoculate

    EC: 1450uS (total, including 300uS base EC from tap water)

    pH: 5.7 - 6.0

    Water temp: 68f-70f


    Is this nute burn? Nute deficiency? Virus? It's progressing faster on the smaller plant that's a few days behind the other one.

    If I missed any information or any clarification is needed please let me know. Thank you for reading

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    Hi cgc420, welcome to the forum, got any pics of the affected plants?
    Last edited by dick_turpine; 14-10-22 at 06:32 PM.

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    Welcome to the talk dude, enjoy.

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    Did you soak the hydroton in ph adjusted water first?

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    Quote Originally Posted by dick_turpine View Post
    Hi cgc420, welcome to the forum, got any pics of the affected plants?
    Thanks! and yes here is the album: postimg[.]cc/gallery/zqPGGMt

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    Quote Originally Posted by Blue61 View Post
    Did you soak the hydroton in ph adjusted water first?
    Hmm, no I did not soak the hydroton in ph'd water, didn't see it mentioned in the guides I read, but I will moving forward! I rinsed thoroughly until the runoff was clear and then for another minute. Should I top feed and check the runoff PH from the net pot to see if that's the issue?
    Last edited by cgc420; 14-10-22 at 09:03 PM.

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    Quote Originally Posted by cgc420 View Post
    Thanks! and yes here is the album: postimg[.]cc/gallery/zqPGGMt
    Here are the pictures individually from that album ;














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    surly that way to strong for a 2 week old plant -- eC 1450

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    Quote Originally Posted by MonsterEnergy View Post
    surly that way to strong for a 2 week old plant -- eC 1450
    I thought target EC is relative? So it would be 1100uS/1.1mS of nutes. Or is that wrong and I need to offset my nute levels for my tap water base EC of 300uS? I'm following this chart:

    Click image for larger version. 

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    Is that chart a bit on the hot side?

    Would you expect to see signs earlier if it's too hot, I was top feeding with the same solution until the roots dropped? What EC should I shoot for at this stage? Thank you all for helping, just trying to get a good understanding of it all!
    Last edited by cgc420; 14-10-22 at 10:05 PM.

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    It’s early days,I wouldn’t worry too much just yet as taking action may be the wrong thing to do.

    I’d let them get a couple more leaves,new growth looks to be good so just keep an eye on things.
    It takes a while to settle in with DWC so the odd bit of leaf damage is inevitable.
    Check roots regular make sure is well there.

    Yes it’s correct to add on the background EC (water) to the target EC.

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