I’m in straight coco, base nutrients are 2-1-5 when mixed, but used some calmag that’s calcium nitrate based when I filled the res, so around 3-1-5 for the last 10 days.
1.8ec, 6ph.
18/6 lights 23-26c and 18-20c at lights off.
300w LED over a 5x5 area.
New growth is mottled in colour and looks excessively narrow, the tips look to be much longer than the older growth. A couple of plants have necrosis at the edge of the leaves, completely different strains. All the stems on every plant are red which I don’t think can be purely genetic, I think it’s a negative response to something.
Low phosphorus can cause the purple stems and yours are only getting 1 P
The overall wonky newer growth could also be related to that, they’re basically trying to grow faster than their feed regimen will let them is my opinion. 1.8 EC is cool and all, I just think your P is too low.
I see leaves curling and perhaps bleached, could be some heat/light stress for lamps being too close? Check if those red stems are only upwards on the top, could just be sun tan …
I did wonder the same thing, I ended up bleaching my last plants with the first run with LED, I’m somewhat discounting light being the issue though as it’s effecting new growth low down on the plant, maybe 24" away from the fixtures which are only set to 100w each (300w total) over a 5x5. I think the PPFD will be below 500.
Reading up I’m now wondering if it could be a Mg deficiency, all symptoms seem to match apart from where everything says it first appears on lower growth. My lower growth looks fine.
Even when it first starts, it’s more of a defined striping in my experience, which again leads me back to them likely being short on phosphorus. Cannabis loves a lot of phosphorus, i believe this is what Bruce Bugbee has stated as well.
That looks like what I see on light bleaching, as in the light is too intense and bleaching the chlorophyll out of the leaves and some heat stress…combine that with a 1.8EC and you might get some issues. What is the par readings? What’s the water source, what’s the EC and PH of it before nutes? What’s the temp and humidity of the room they are in? More Phosphorus like others are saying…but personally I run a little more N even in flower to keep the leaves nice and green so they function correctly.
No offense @Taproot but the o.p. did a decent job laying all that out, except for the EC and pH of his water prior to nutrients not sure why that matters
So, I was just chiming in confirming what somebody else said about it looks like light burn / heat stress cause its happened to me more than once when I went from hps to led. I found through personal experience brightness isn’t a measure to ballpark something with leds like hps and more isn’t always better which is why I asked about par / ppfd. He states he thinks it’s below 500. I’m just curious what the basis for this hypothesis was made…maybe using one of the phone apps? I found the apps to be way off for me until I calibrated them. But, again what I found personally was when I bleached the leaves it caused other systemic issues that seemed like nute issues but were not.
Humidity is also important, he says 78F or so which might be a little low for leds if the humidity is also low due to the vapor pressure via lack of IR from leds. Also, starting PPM and PH can be useful info especially if it’s well water. For example mine was 40 ppm at 4.9PH so it’s pretty void of cal/mag which helped me to know I had to double up in coco vs the city tap I was using. I also have a lot of sulfur so I found silica helped lock in ph. All that added up before nutes so I like to have ppm before so I understand how much NPK I’m giving as I was under feeding and didn’t know it until somebody asked what my staring ppm was.
I missed the temp part sorry…but I’m just sharing what others have helped me with. Didn’t mean to intrude.
0.15ec, 6.8ph, municipal water, this does gas off and climb 0.1-0.2ph after mixing nutes.
Humidity is 65%~ during lights on, I meant to put that in the first post.
My way of estimating PAR is somewhat convoluted but I think the method is relatively sound.
I went off the PPFD measurements given by the manufacturer, they are just QB288 boards with LM301H 3K diodes, there are plenty of independent tests that were showing very similar figures and
looking at the binning available from Samsung there isn’t a much variation at all meaning I could compare them to more reputable companies like HLG. It suggests any number fudging by the OEM manufacturer I bought from is minimal and if it’s max PPFD I’m worried about then it would only work in my favour as a safety margin.
With that in mind I compared readings with the photon app which were about 10% lower than PAR tests I could find online. My understanding is that a sensor in a phone while not accurate at estimating PPFD is extremely repeatable and the measurements are linear, so if I’m 10% out I should be 10% out everywhere I take a measurement.
The plants fill a 5x4 area and I have 3 fixtures over them pulling 300w total from the wall. With the phone app I’m getting measurements of 350-450PPFD across the area.
My guess is also toward a tad too much light. Red stem can be sun tan.Look at the underside of petioles to check. If they’re green, sun tan. It does not seem too much though, just a tiny bit lower light level should do it. Just test it, you’ll even save a bit of money and see quickly if you’re phone PAR meter is worth it
What phone are you using Android or Iphone…on Android I’d suggest using the PPFD app and pairing it via BT with this cheap lux meter. It’s been reviewed a lot on youtube by guys that have $500 par meters and it was very close. I’d not rely on the internal sensor on the phone on Android.
Other than a calmag def and or light burn…I did have to put a little N in the mix when using something like dynagro to keep healthy green leaves which IMO is important from seed to harvest. Uncleben here talks about it a lot from what I remember. I’m using maxi right now and still put a small pinch of maxigro into the bloom feed for more of a 6/7-15-14.
Hey bud, great looking plants. Personally I would back the light back a bit. looks like a little light stress I my opinion. Like they are being over driven a bit.
while ppfd is great and can get you in the ball park, without a proper meter its so hard to tell.
Take a look into DLI “Daily Light Integral”
they may just be getting to much light over the 18 hour period.
Example my 24 hour veg is much dimmer than my 18 hour veg. you will be amazed what deficiency you can affect by just changing your environment.
I just feel like the lights are really not that bright.
My fixtures are spread out and are giving a very even output over a 5x5 area, there are no walls on 3 sides so there is a lot of wasted light spilled, they are also 12-24" above the plants. I was only running them at 300w total, that’s 12w/ft probably closer to 10w/ft with the lack of walls, even at 18/6 that shouldn’t be causing excess DLI surely. I used to veg at 40w/ft with DE HPS without issue, I know LED are more efficient but not by 400%.
With that said, since turning them down yesterday to 250w they already look better. So people saying they were light stressed are probably on the money, but I don’t think light levels are the root cause.
I’m mixing up a new nutrient res today, using some old bottles of canna.
Well maybe the nutrient level wasn’t hot enough to feed the added chlorophyl intensity? Lacking CO2 maybe?
I’ve been quite surprised by the LED efficiency myself, same symptoms.
The amount of light a plant can handle is also very dependent on the cultivar, some are really sensitive. Could be that, given not all of them had that symptoms.
Check if those red stems are only upwards on the top, could just be sun tan … 
