OF needs some advice

[Olderfart]

@Mañ'O'Green, it seems as though in spite of my efforts, it is my turn to ask for your help.

-Problem: girl eating lower fans, some stems still a bit light color, others not, beginning of nute burn in spite of light color.
-Medium/grow method: SS#4, plus ~30% perlite in most of pot, plus ~50% in the autopot flood zone in the ~5cm or so in the bottom of the pot.
-Feed and supplements used: MC version two, cal mag. some BE lately, yucca, fulvic.
-Water source: Melted snow, EC ~30-40
-Strain and age: Seedsman Auto Strawberry Cheesecake now at day 47.
-Climate: Temps controlled at ~24C (max ~28, min. ~21) day and night, RH almost always between 40 and 55%, with brief excursions to either side.
- Light used: Diy screw in array, mix of 5000K and 2700K, currently at ~ 450watts total for ~9 sq ft, array over STCH is ~33" from top of canopy.
-Additional info: Issues with this plant have been going on for a while. The history is as follows:

- gradual increase of nutes from ~360EC to ~750EC by day 35. pH started at ~6.5, and was at 6.2 by day 35. The nute mix was primarily MC with cal mag accounting for ~20% of final EC. A bit of fulvic and kelp was added to the mix later. I saw hints of mag deficiency, hence the cal mag.

- By Day 38, the plant was showing light green new growth, and light green lower fans. Given the relatively low EC input, I suspected a lockout caused by nute imbalance/overfeed, or soil pH issues, so I flushed with multiple volumes of pH'ed nute mix to get the medium into spec. PH of the runoff was fine, I thought, at ~2.3 which was pretty much the same as input, but EC was >1450, far higher than input. I figured that I needed to get the EC down, but did not want to overdo it at once, so I flushed to ~950EC, and then did a final fertigation with fresh mix at that strength. The new mix was ~55EC Cal Mag, 600 EC MC, 220 EC BE (flowering now well started), 35EC kelp, fulvic, and yucca, mixed in ~40EC water. Once this was top watered in, the plant was left to dry out.

- Mix since the flush has been ~950EC, pH varied deliberately between 6.25 and 6.4.

- It is now day 47, and the colour of new growth has not improved, and she is still eating lower fans. To make matters even more confusing, today I see initial signs of nute burn on this plant and its neighbour on the same reservoir. I now suspect that she is locked out from being overfed instead of underfed which might otherwise account for eating the lower fans. Absent contrary advice, I will likely flush her again, and take the mix down to ~750 EC, all MC with a bit of BE.

--Pictures

The whole plant:

The lower fans:

The worst fan at the moment:

Thanks for any assistance you can provide.

 

[Mañ'O'Green]

The lower leaves are not a worry. You have stressed the plant some with flushing and the such. Some of your numbers do not make sense to me? Please go over them again and edit in PPM in the Hanna Scale. It looks like you used EC for PH numbers? Snow should be 0 PPM or close. Are you near a highway or down wind of industrial plants? Expand SS#4? I don't know what this is.

Tag me with the answers.

 

[Olderfart]

My numbers are all EC in micro siemens rather than millisiemens, so appear to be 1000x the figures in your table, but are the same concentration. Divide my figures by two to get Hanna PPM. On the whole, I figured my concentrations were low, but I am definitely seeing the beginning of nute burn at the current ~950EC.

SS#4 (Sunshine #4) is a peat based mix similar to Pro Mix HP. It has dolomite lime in it to buffer pH, and has perlite, but I added more to make sure that the pots are well aerated, expecially in the zone flooded by the autovalve. Nutes if any in it are very light, it is not pre-loaded to support plants for much beyond germination and initial growth.

The flushing was ten days ago, would that still be showing up as active eating of lower fans now? I should note that I do not flush with plain water, I do it with pH'ed and EC controlled nute mix to minimize shock. Also, she was eating lower fans before the flush as well, which was part of the reason I flushed, the other part being the light color of new growth.

At this point, I am suspicious that I left the EC too high after the flush. I was interpreting the loss of lower leaves as a potential nute deficiency, when it may not have been. Since she is well into flowering, I was assuming that my EC was low for that stage, and given the light color on most new growth, figured I needed higher. Seems, perhaps, that I did not.

If you figure that I am dealing with lockout caused by over fertilization, my decision is how to fix it. I am tempted to flush again with nute mix at the EC and pH that I want the medium to be at, but am keen to hear what you suggest. I don't have a soil pH meter, but my earlier flush showed zero indication of pH drift in the medium. What came out was pretty much the same pH that went in, ~6.2-6.3, and I checked it several times during the flush. The reservoir has been kept at 6.2-6.4 without fail since the flush, and 6.2-6.5 before then.

As to the melted snow, it varies in EC, but I think the issue might be organics from plant debris, or dust accumulation brought in by it. The area I collect it from has needle fall from conifers, and scraping up the snow sometimes includes bits of plant debris as well. I did measure it as low as 10EC once, but not since then. Now that we have more snow, the EC will drop because I will not have to scrape it up off the ground. I am in north central British Columbia, so other than wood smoke once in a while, air pollution is unlikely to be a potential source of contamination.

Thanks for getting back to me @Mañ'O'Green, I appreciate it. Above and beyond on Dec. 24th!