Rusty-colored leaves: Deficiency or Fungi??

[TimeTraveler]

Hey all! Got a pair of plants that both have rust-colored discoloration and patches on their various leaves.

They both were losing color and dropping lower leaves due to what appeared to be nute deficiency, but after some serious feeding over the weekend (and some foliar spraying to wash off some tea that had dried on the leaves), the plants have regained their lush green color but rust coloration has arrived on the leaves instead. I've tried rinsing or gently rubbing to see if it would come off (thinking maybe it was some oxidized soil or something from that tea that had refused to rinse off), but no dice; it stays.

After some preliminary searches the three most likely culprits seem to be Cal-Mag deficiency, Boron deficiency, or fungus. They've both just started into flowering, so I really, REALLY want to handle this so they can produce nice, fat buds for me. Pics follow:

Help a novice out, AFN. We're counting on you up here on the Moon; our advanced technology has failed us!

 

[Wienerwoods]

Could it be burning from the liquid droplets on the leaves? Whenever I foliar feed, if it's stronger than water it will burn the leaves, even if I rinse it off. And it starts to show long after the spraying.

 

[TimeTraveler]

I don't think so; I try to let the plants air-dry before returning them to the lights after a foliar feed (I spray them outside the box so it won't spot on the mylar and ruin the light reflection). There are like one or two sugar leaves that have tiny pin-prick holes in them that appear to be from light burning through when I did put the plants back a little wet (over a week now and they haven't grown or appeared elsewhere, so I'm ruling out caterpillars). I'm fairly certain it's a deficiency of some kind, but I'm worried that maybe the feedings followed by the rinsing left them wet enough for fungus to take hold on the leaves.

 

[Renaissance Redneck]

After some preliminary searches the three most likely culprits seem to be Cal-Mag deficiency, Boron deficiency, or fungus.

Traveler, Boron def is fairly uncommon, and typically will show in the upper leaves first.
It looks like a lot like P def, with maybe a lack of Ca as well. Can you post a whole plant pic?
Now the questionaire:
How often and how much do you feed and water, and what nutes are you using? NPK analysis, and how much how often?
Soil type?
What is your soil pH, grow temps and RH?
If you have a strong magnifier, take a look where the spots meet healthy leaf tissue. If it's a fungal problem, you should be able to spot a line of advancing spoors.

 

[TimeTraveler]

It looks like a lot like P def, with maybe a lack of Ca as well. Can you post a whole plant pic?
It's two plants, but they're sharing a planter and, unsurprisingly, showing the same symptoms.
The Massive Midget:

The Sugar Black Rose:

How often and how much do you feed and water, and what nutes are you using? NPK analysis, and how much how often?
I water as needed (going by the second knuckle test), typically two to three times a week; usually about one to two quarts of RO water. I fed for the first time about a week ago, using a compost tea cut with RO water (about a pint cut with the quart and a half of RO water), some liquid kelp with chelated iron (about 1/4 C mixed into the tea/water mix), and then put down about 1/4 C of dry nutes before topping the planter with fresh soil. The nutes I used are Down To Earth brand All Purpose dry fertilizer (4-6-2).

Soil type?
Organic super-soil mix, hence why I hadn't fed it before now (it's fairly rich; my last grow went from seed to finish without showing any signs of deficiency, but this grow is bigger and healthier so I imagine they're eating more).

What is your soil pH, grow temps and RH?
Last I checked it, it was 6.5 although I don't have a soil pH probe, so I have to do soil/water slurries or measure runoff. pH shouldn't be an issue in here, as super-soils tend to be much better at keeping a stable pH, but obviously I'd never rule it out. Grow temp is about 79F, RH 55%.

If you have a strong magnifier, take a look where the spots meet healthy leaf tissue. If it's a fungal problem, you should be able to spot a line of advancing spoors.
Don't have one yet, but I was planning to buy one in the next couple days for trichome inspection.

 

[Renaissance Redneck]

Nice pics!
The RH could come down a tad now that you're in flower, 35 or 40% is a good number to shoot for, mainly to guard against bud rot.
With the tip burn, I'd say your really pushing the N
Some of that does look like splash on the leaves, but to me it still looks like Ca and P issue.
In flower, you may want to find a nute with a higher P-K ratio, something along the lines of a 2-6-8.

 

[TimeTraveler]

Thanks for the advice! There might be some splash on the leaves, but most of it rinsed off last week, so I'm convinced most if not all of it is nute deficiency.

I might have some higher P and K amendments sitting around; if not I'll head to my local grow shop to find some organic supplies to fix her up right, and maybe some Cal-Mag to be on the safe side.

 

[Waira]

Hey Time'-- Hmmm,... I'm thinking this is not a defc. issue, but fungal, I'm afraid... that second pic down, with the really oddly rust colored leaf, not fully dead tissue yet either,... the nature and pattern of spotting/dead patches on then other leaves,... doesn't fit any defc. well at all,... P defc. can take out larger patches of tissue, but it has a distinct "wet" look to it, soggy wasted tissues,... this doesn't have that look,... and treatment options, in bud, are very limited,... top plant is young enough to take pure neem oil, but the MM below might be too far into bud,... I have to chat with a guru about this, ASAP.... hoping I'm wrong, friend,... .... stand by, he's not on right now,...

 

[TimeTraveler]

Well, to be on the safe side I'm adding some bone meal (1-15-0) into the soil, and I've got some organic, non-toxic fungicidal spray recipes from other forums that people swear work during flowering (one uses baking soda, the other garlic, can't personally vouch for either effectiveness).

I'm not certain it's fungus, as when I rub the leaves nothing comes off or rubs off, but I've found people saying both that it will and won't rub off if it's fungus.

The only thing that makes me think it's definitely a nute deficiency is that last week I had a LOT more discoloration on the plants that was solved after a heavy feeding; my guess is that now that I'm in flowering they still need more P, and the micro nutes and N and K issues were resolved.

 

[A4]

Very strange and at first I was going to say it looks like P. The longer I look, like Waira, I don't think so either. It isn't going to hurt to give what you did TT but I don't think it will help that problem we are seeing.

There is a red bacteria that occurs a lot in water, can't remember the name off the top of my head but it is something like cyanide. Anyways, I have seen that quite a bit in older water that is stagnant. I don't think that is it either really though. I see it in DWC a lot but just curious with the foliar feeding if something like that could have infected it.

I foliar feed a lot, all the way up to harvest and have never experienced anything like this symptom. If I had to guess I would think it is fungal or bacterial and probably has something to do with the foliar feed, tea, or something in the area that has been compromised. Honestly I am not too sure how to repair it either. My immediate thoughts are a weak hydrogen peroxide solution but I have only used that when washing my plants after harvest. This is the one time I don't think I have any advice I can offer to improve the grow my man, and that is rare. Keep us informed of the progress, I am going to see if you have a journal and follow along because I want to know how this turns out.

My one suggestion would be, when you have harvested, go through all of your equipment and use a 10% bleach solution and wash everything down. All your tools, your water buckets, the inside of your tent or grow room, your containers. Saturate everything in a good washing. I am afraid if you don't, you may continue to see this on future grows.