Double Grape, Double Troubles.


Oct 3, 2016
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Problem: Progressive browning/curling on fan leaves. Seems to be starting with the older first.

Medium/grow method: 2 gallon Hempy bucket w/100% Growstones for the growing medium.

Feed: and supplements used: .5ml Armor-Si/7g Maxibloom/10ml CALiMAGic/1ml Mammoth P per gallon. Older plant is currently on day 3 of usual feed + 1.2g dry KoolBloom powder per gallon. All nutes are PH'd to 5.8.

water source: Tap water (usually rested overnight but the past week or two I haven't bothered. not convinced chlorine is enough of a concern to worry about)

Strain/age: Mephisto Double Grape. Older plant is on Day 50, younger is on Day 38.

light used: 55W Autocobs x 2

Climate: Temps: High 70's-Low 80's. Humidity: High 40's-High 50's.

Additional info: First noticed a leaf on the older plant with light brown spots maybe a week or two ago. I've had PH issues in my past two grows and this didn't look like those instances of PH swings so I wondered if it was simply my plant starting to eat it's own nutes and decided to wait and see a bit. The spots continued to brown out and still didn't look like the necrotic spots I'd seen in older grows so I let it go a little longer, then the leaves began curling and I figured I better ask for help. :yoinks: I believe it to be a P deficiency, maybe a K problem. The medium I'm using is made with calcium carbonate which apparently makes up 1.25% of the final product itself, so I wonder if the calcium from the Growstones is kicking things out of wack and causing issues with P or K. There looks like there's a slight bluish tint to the leaves of the older plant as well, but I could be wrong. Any thoughts would be greatly appreciated!





These last two are the younger plant. Sativa pheno, if that makes a difference.

I would say that you should get the chlorine out for sure. It does look like a P / K issue but im not experienced enough diagnosing to give a positive answer.
I would say that you should get the chlorine out for sure. It does look like a P / K issue but im not experienced enough diagnosing to give a positive answer.

Based on what I've read chlorine isn't nearly as much of an issue as most think it is. I'll have to go back and find the links but I did some reading over the past couple weeks and from what I've been able to find there have been a few studies done that show that while chlorine *does* have an effect on the bennies in a soil or hydro grow the overall effect is negligible in terms of overall bennie health/populations over time. Just for giggles though I upped my Mammoth P dosage from .6ml/gallon to 1-1.5ml/gallon to compensate for any die-off in my nute solution from the chlorine, and while this certainly isn't scientific the gallons of nutes I've been mixing up with the fresh tap water and extra Mammoth P have had the same "bennies funk" smell as the nutes I was mixing using off-gassed water. Of course I suppose that doesn't mean that it couldn't have an effect on other elements in the nutes but I don't know if there's any data on that.

But yeah - P or K was the only thing I could come up with too. The PH swing issues I had on previous grows produced a gray/blackish necrosis and never caused leaf curling like I'm seeing now, but the P/K deficiency pics don't quite match up either. Seems the most likely though, in my limited experience.
:toke:-- yeah, this looks like a P issue, an uncommon manifestation of it,.. another grower had very similar issues and symptoms, likely for some sort of pH drift,... check it out--
......... weird, it has to be pH related-- temporay lock-out?...., what with the abundant PK you have going in,... :shrug:
Yeah, is that the pic from the quick reference/diagnose-your-own thread? If so, that's the thing that really cemented it in my mind as having something to do with P versus anything else - the earlier stage of it looked almost identical, then it spread to the rest of the spaces between the veins and the leaves began to curl.

So, here's the question - I've been careful to keep everything at 5.8 when I mix nutes. How likely do you think it is that the calcium carbonate in the medium I'm using contributed to some kind of PH swing in the reservoir, or a lockout some other way? The growstones come pretty dusty, even though I rinsed/PH balanced them I wonder if there's not still some leaching going on.

Also, last question (as far as I know, lol) - my younger plant that's 12 days behind is showing the same symptoms, only the very beggining stages. I have some liquid KoolBloom that I was planning to start using with my coco grows after this one wrapped up. Would it help to make a new batch of nutes and throw some in to make sure my younger plant doesn't end up like the older sister? And if so, how much per gallon would you suggest?

Thanks for stopping in, Waira. The advice/insight is invaluable! mean the growstones? that's a clay material, they should be pretty neutral and not leach anything,... I don't think the Maxi' line is self buffering like AN is,.... so pH is going to drift,.. what's the water pH and ppm/EC? ... this has a direct influence on pH buffering as well, depending on the numbers,.... also, a ppm/EC reading of your nute solution would help too,.. since you're basically hydro, these tools are essential in dialing in your feed strength and managing inputs,... see, I have no idea how much Xgrams of nutes translates to ppm in solution,... it is odd you have defc, symptoms, but it might be because of a pH lockout, not lack-of--

... no, don't up the PK like that during veg', the grow has enough,...
you mean the growstones? that's a clay material,

Nope, not clay at all. It's made from powdered recycled glass. Their site says the final product is 98% glass, 1.25% calcium carbonate. Hence why I thought they might be the cause of the P issue - I read that an abundance of Ca. can trigger P problems/lockouts. As for PH of my water itself, I think it's around 8 before nutes and such but it's been forever since I've measured it specifically. As far as TDS/EC, I have an el cheapo TDS meter that I hardly ever use, just because I have a feeling it's not all that accurate. I've only ever just been making sure the nutes I feed are 5.8 after everything's said and done.

PH drift and all that it can affect are new to me - I've heard of it, I know basically what it means, but could stand to read more. Any threads or sites or books you suggest? I've never had an issue this severe before - though I'm sure I could have done something about it sooner, lol.
... no, don't up the PK like that during veg', the grow has enough,...

I didn't! Both plants are in flower now - one is 51 days, the other about 12 days behind. Older has been getting dry her usual feed + KB since the 28th of last month, the younger just got started on her usual feed + liquid KB tonight.
...roger that, they're fine in any case, the CaCO3 is locked in,... yeah, too much Ca can interfere with other nutrients' uptake, but it has to be rather high, and the pH would be FUBAR to get there anyway,...
well, the pH once set, isn't going to stay stable for long,.. but water that has some hardness to mit, and Ca-Mg, have ca carbonate in them, the carbonate is whats' involved with the pH buffering in solution,... have you calibrated you pH meter recently, or store it in proper storage solution? They go out of calibration easily,... at around 8 on your tap, it sounds pretty hard, high mineral content,...
I have to write a little piece on pH buffering and all that,... no threads here really, just google "pH buffering in water" and you'll find some basic info about it,... there's a diagram in the Defc. Pic depot here, 2nd page that shows some of the reaction chemistry,....
well, the pH once set, isn't going to stay stable for long,

How long, on average? I mix mine a gallon at a time and between the two plants was making up a fresh batch every three days or so and watering ever day. Now I'm mixing them separate batches (as of the 28th) because they're each getting different types of KB.

As for my meter, I do keep it calibrated about once a month though I do need to re-order some more 4.0 reference fluid. And I always keep it in the storage liquid.

And don't quote me on the 8 PH water out of the tap - I only measured the plain water once and knowing my brain lately I could be mixing it up with when I was still buying water, lol. Memory is not always my strong suit! The TDS meter I have does peg my plain tap water at 140-146, but again, not sure if it's accurate.

Can you recommend an EC meter that's not abhorrently expensive?