Olderfart back for advice again - Iron deficiency?

[Olderfart]

Problem: yellowing leaves

Medium/grow method: ~1 gallon coco/perlite, automated top irrigation to runoff.

Feed: and supplements used: Jack's 321, Jack's Clone, Jack's bloom. Currently at ~1450 EC 321, recently increased from ~1350. PH ~5.8-6.2, usually at the lower part of this range. Never outside 5.7 to 6.5.

water source: surface water from creek, ~60 EC, will be declining as I add snow melt over the rest of the grow.

Strain/age: Dinamed Auto CBD Kush, Day 44

light used: DIY screw-in array, ~1/2 2700k, the other half 5500K, ~600mmols ppfd, 20/4.

Climate: ~26C, 45%RH

Additional info: Plants were perfectly healthy and vigorous until well into flower, then some central branches started to show yellowing, and it has become worse in the last few days.

Here is the pot, it has 3 plants in it:

Note the lighter colored leaves on some of the colas.

Here are a few closer shots:

The plant is doing well overall, at least it has been until now. The discoloration only affects part of the plants so far, but it seems to be spreading. It seemed to start mostly in the central area of the pot, while the perimeter colas stayed darker. More on newer growth than older, but the oft described progression from the base of the leaf to the tip is not obvious.

It looks a bit like an iron deficiency, but maybe not quite right. If it is an iron deficiency, what should I, or can I, do about it at this stage. I think the plants have only about 3 weeks to go. If correction is useful, it will have to be with locally available products, which may be a problem. If it is iron deficiency, odds are that the other plants now younger than these will be headed for the same problem so it would be nice to figure it out.

Thanks for looking, and for any help you might have to offer.

 

[DCLXVI]

Hmm, what's the measurements on your nutrient mix? How much of each part are you using gram/gallon I mean.

Did you use "bloom" on it's own? How much/how long did you run it?

Do you have their "finish" product?

 

[Tom Bombadil]

Almost looks like its genetic... @Mañ'O'Green might have an idea.

 

[idiopathic neuropathy]

I think you will have to ride that girl into harvest.
I have experienced this same condition twice---- one time it was two Blueberry cookies from Dinafem where one plant was green and fine, while the other yellowed like yours. When it first started to yellow I thought it was a magnesium deficiency and treated it with more magnesium. It continued to yellow so I flushed, but she continued to yellow. The second time it was a 4 plant grow and one plant yellowed like that and couldn't correct it. The 2 different grows it happened I used 2 different nutrients ---one was Jacks321 and the other grow was General Hydro Flora Trio both autopots.
I could never figure it out. Maybe it was lockout in its' early growth stage.
Hope you or The Mañ'O'Green figure this it---still curious.

 

[Waira]

OF me brudda! Hope you're doing well....

Hmmm, don't think it's Fe, right on the pattern not being a good fit. As a general rule, when the tops fade first and worst, it's very likely some sort of immobile nutrient defc., the trick is figuring out why!
...lockout by pH and/or antagonistic uptake (see pg.2 in the Defc. Pic Depot here in the Sticky section on top; charts will show what I mean), or plain old lack-of...
Looking at the ppm (not EC mate; depending on the scale, 1.0EC = 500 ppm), and the later stage of bloom here, I'm leaning toward some antagonistic uptake issues, meaning the Fe ions are getting "crowded out" at uptake sites despite Fe having a strong +charge....

Recall, the girls are on the downswing for nutrient needs and uptake now, so strong inputs may cause complications,...
Do you test your run-off for pH and ppm's? This offers some vital info about possible build-up and such...

** damn, I have to go to work now, BBL though!

 

[Olderfart]

Thanks for the feedback everybody, I appreciate it.

@Waira , my runoff has been high, and when I measured it, pretty much the same pH as going in, and lower EC. But I will check it this morning and get back to you, it has been a while since I bothered. I will check it on a couple of the other larger plants too to see if this has gotten away from me since I checked last. I have been assuming that my excess runoff would take care of any buildup or balance issue (I suspect a fair bit more than 20%).

 

[Weedname]

Hello @Olderfart

I see that they have enough Nitrogen but lacking both Calcium, Magnesium and K.

At first i thought it was cold root-temps (not 26C as stated) but after reading i got a better picture of what was going on.

Want to share a pic of what the bottle of nutrients contains?

Oh, how much light do the flowers get?

 

[Olderfart]

Hello @Olderfart

I see that they have enough Nitrogen but lacking both Calcium, Magnesium and K.

At first i thought it was cold root-temps (not 26C as stated) but after reading i got a better picture of what was going on.

Want to share a pic of what the bottle of nutrients contains?

Oh, how much light do the flowers get?

PPFD is ~600, hours are 20/4. Nutes are Jack's 321, specs are online if you want them, but leave it with me, my initial checks this morning suggest that I have an oddball pH problem. I am still working on it and will report back.'

Thanks for the feedback.

 

[DCLXVI]

I would not worry about runoff pH, just input in range. Nice thing with coco is it can be effectively flushed and corrected. I know you know.

I had some odd problems crop up when using the Jacks Bloom hence my curiosity about it.

 

[Olderfart]

Well peeps, the puzzle may be solved. When I checked runoff this morning, pH in runoff from two of the large pots was ~4.2. That would be four point bloody two! I had monitored pH and EC in runoff for a couple weeks earlier on, and it seemed that the only pH issue was that the reservoir would drift upward gradually for a couple days, so I would start it at ~5.8 and let it climb after that. That usually meant that it would stabilize in range (5.8-6.2). None of my runoff was significantly different than input, so I backed of monitoring the runoff. Since I fertigate to more than 20% runoff, I figured that little mischief in the medium was likely. Seems that I was wrong.

Anyway, all large pots have been flushed with nutes until pH of runoff was in range, then flushed one more time with fresh nutes at ~pH6.3 and 1250EC. I will see how things go, monitor my runoff, and set the input pH higher than I have been.
@Waira, have you heard of coco drifting to lower pH? I had no idea that it would do this.