Small, rapidly spreading purple spots [+pics]

Discussion in 'Sick Plants and Problems' started by ForgetfulFrog, Nov 25, 2011.

  1. Hi guys,
    I'm thinking I have a phosphorous deficiency here, but would very much appreciate any feedback (it's a long trip to the nearest hydro store...). As you can see in the pictures, I have a lot of small purple-ish dots/blotches on a few leaves, the stems are purple, and the plant is quite droopy (though she perks up after a water/feed, she begins to droop again within 12-18hours). These 'spots' appeared approx 24hours ago, though the drooping started 3 or 4 days ago.

    Indoor, coco/perlite (70/30) grow (11ltr/2.5gal pot). Feed consists of H&G A&B and some epsom salts. EC going in equals run-off EC. Water is (hard) tapwater with high calcium levels. Water/feed once per day. Under a 250w red spec cfl, with some additional lighting from a 125w blue spec cfl. High humidity, temps around 18-25'c (65-80'f). She's a Lowryder#2 approx 42days since germ began, and has been flowering for just a few days.

    Cheers for any input.

    Attached Files:

  2. if your EC going in is matching your EC coming out, than that is NOT good. that means nearly 100% of what you are putting in is getting leeched. try giving your soil some humic acid. it will help with nutrient abosrption & improve uniform watering of the soil. use humic acid about every 2 weeks & give it nothing but H20 and humic acid when you water.

    you are watering too much. water when the soil becomes dry. i can usually look around my room and tell what needs watering and what doesnt, but a good way to test this is to lift up the buckets to feel how light they are. if it feels quite light than you know they're thirsty!

    the pH may be a little bit off, too. it depends on if the new growth recovers after you let your soil dry out. if it doesnt, its pH. anyways, it looks a bit low (acidic). before adding nutes or humic acid, make sure your soil's pH is above 6.5. i say 6.5 because i also believe your plants arent absorbing an efficient ammount of phosphorus and magnesium. some epsom salts & phosphoric guano should clear that up. but again, they are unavailable to plants with a pH lower than 6.4-6.5. get that pH in range before you do anything.
  3. Thanks for the response Buckeyes,
    However, I'm growing in coco coir and perlite (70/30 mix) rather than soil, and so I think it should be near impossible to over-water and watering daily should be okay - or so I've read.
    I'm under the impression that (in coco/hydro) if the EC going in matches the EC coming out, she's eating as much as she's drinking - if the EC is lower, she's eating more than she's drinking, and if it's higher, she's drinking more than she's eating. Based on that concept I think I have the feeding/watering balanced roughly correctly. Of course, I could be wrong when applying that theory to the in/out EC....

    You do mention something I forgot to put in to my opening post - pH - I'm feeding/watering with 5.7-5.8 pH every time (comes out around 6.2-6.4) - which I understand is okay (use a bluelabs combo meter for measurements).

    I think you're correct in thinking there's a phosphorous and possibly mag issue going on - I am feeding epsom salts but I don't have anything, other than the coco A&B feed, for phosphorous, and since she's entered flowering recently and these purple spots are very recent, it makes sense I think. The only thing that throws me off the phosphorous idea is that symptoms of phos def apparently include slow growth but she's grown more in the last few days that ever - at least a couple of cm taller each day - a bit strange.
  4. thats strange.

    well the weird clawed growth is due to pH. your medium is to alkaline, try to make it more acidic. the highest you want your hydro pH to go is 6.0. with the runoff being 6.2 or higher it means your root zone pH is higher than 6.2.
  5. Seeing as it's been a week since I made this thread I thought I'd return with an update.

    I think the problem has been solved, so hopefully anyone encountering similar issues might find this useful.

    After this thread and a fair bit of researching on forums and the like, I decided the issue was most likely a deficiency, probably P/K related.

    So, I made a visit to my local hydro shop and purchased some bloom/flower coco A&B feed (H&G again) and also some H&G PK13/14. The PK13/14 has been used as a nute supplement rather than for the '3-4day boost' it's advertised for.

    Her previous feeding details (per 2ltr water - daily):
    1.5ml coco A&B grow (combined 1.5ml, .75 of each)
    1 or 2 pinches of epsom salts
    for a total of 1 - 1.1 EC (very hard tap water, 0.7EC from the tap)

    Her updated feeding (per 2ltr water - daily):
    Started at 2ml for 2 days, then 2.5ml for 5 days, and just started on 3ml H&G coco bloom (again, combined A&B measurements)
    1 pinch epsom salts
    1ml of PK13/14
    for a total (at current 3ml/1pinch/1ml per 2ltr) of 1.2-1.3EC (again, inc water #s)

    The result has been very good I think. The purple/black/necrotic spots have stopped spreading and she has taken off - probably doubled in height in 7 days!
    It seems clear she was being significantly underfed and that exasperated her deficiency issues.

    The attached picture (camera phone, sorry) is from 7 days after the pictures in the opening post.

    Attached Files:

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