Brownish mid-aged and young leaves, yellowish fan leaves

[TonyGr]

-Problem: As shown in photos, a couple of mid-aged leaves have brownish spots, like skin cancer. Some mid-aged and young leaves have those lighter brown marks all over their surface. And finally lower fan leaves are yellowish.
-Medium/grow method: Soil. 20% Biobizz Light Mix (top), 80% Biobizz All Mix (bottom).
Airpot 11 liters
-Strain and age: Blue Cheese Automatic (Royal Seeds Queen), 6 weeks and 5 days old
-Feed and supplements used: Root!t First Feed first 20 days. Since third week Bio-Grow and Top-Max. Some Alg-A-Mic the third week. Since fifth week Bio-Bloom and sixth week Bud Candy. Finally 2ml of Sensi Cal Mag Xtra just the fifth week.
For example last time I watered I used 2.6l of water with 2ml Bio-Grow, 2m Bio-Bloom, 2ml Top-Max, 4ml Bud Candy and 2ml Alg-A-Mic. Today I will use plain water and 2ml Alg-A-Mic again hoping the plant to recover

-Water source: I use tap water mixed with rain water (always dechlorinate just in case). I adjust pH using lemon juice around 6.5 to 6.7 pH. No EC/TDS meter available so far
-Climate and Light Schedule: Lights 20/4. Humidity 40-50%. Temps 18-21 Celsius when lights off and 20-24 Celsius when lights on
- Light used: 1xLED 18W 1850lm 4000K and 8xLED 12W 980lm 3000K. Distance to tops 20cm
-Additional info: Yellowish fan leaves maybe is normal. My baby is getting old I guess Dark brown spots are just a couple. So, I worry mostly for the light brown marks that affect mid-aged and young leaves and seems to get worse day by day.

Thanks again in advance

 

[Rev. Green Genes]

I think Iights are too close for one thing, 20cm is very close, even with low wattage lights. That can be overcome somewhat with sufficient airflow, but even then I would go 30 or more cm. Especially during a recovery period. My guess for the main problem is your pH is off. You have a combination of issues here and I am not sure if it is a deficiency or a pH lockout. I think @Waira would require you do a pH test before you could determine how to fix it. Are you using a pour through test? or do you have a soil meter?

Whenever I see crisp lines around the discolored spots, I immediately think virus. Because in the gardens I work for that is usually what it is. Mosaic type patterns for example. One of your spots have that appearance a bit, but I'm still guessing you have lockout.

 

[TonyGr]

I think Iights are too close for one thing, 20cm is very close, even with low wattage lights. That can be overcome somewhat with sufficient airflow, but even then I would go 30 or more cm. Especially during a recovery period. My guess for the main problem is your pH is off. You have a combination of issues here and I am not sure if it is a deficiency or a pH lockout. I think @Waira would require you do a pH test before you could determine how to fix it. Are you using a pour through test? or do you have a soil meter?

Well thank you for your answer! I will adjust height and fans accordingly. So far I measure pH before I add nutrients. I trust Biobizz soil to keep pH in range.

 

[Rev. Green Genes]

The buds are coming along nicely, and she looks like she wants to recover to me. For the most part, all soils and mixes require some tinkering with the pH. The nute manufacturers cannot guarantee the final pH unless they test it with every combination out there. They can get you close for sure, but every thing added, and all parts of the media, each will interact over time and the chemical bonds and formulas for whats in the soil itself changes.

 

[TonyGr]

Well, an update. I measured the warer surplus pH (I don't know the correct word in english :S ) after watering and it was 7.2

 

[Rev. Green Genes]

Well, an update. I measured the warer surplus pH (I don't know the correct word in english :S ) after watering and it was 7.2

I will repost Waira's pour through test instructions here.

* first, test the pH of your usual water source*
1. water containers to saturation (so that a few drops of water come out of the bottom of the container) with the normal irrigation water they have been receiving... do not use a nutrient solution, it will badly skew the results...
2. after container has drained for one hour, place a saucer under the container -- make sure to use a clean, uncontaminated container- any residuals in dirty one will skew the readings,....
3. pour enough distilled (DI)/RO water on the surface of the container to get about 50 mL (1.5 fluid ounces) or so of leachate to come out of the bottom of the container (Table 1)
4. collect leachate for pH and EC testing;
5. calibrate pH and EC meters, if not done recently
6. measure pH and EC of samples, then do this calculation-->

-- Calculation ->>> If your runoff pH is higher than your starting (water) pH, use this equation to determine your soil pH:*
Soil pH = Runoff pH + Difference

--- If your runoff pH is lower than your starting pH, us this equation:
Soil pH = Runoff pH - Difference.

For example, say your the starting pH of your solution before it goes in is 6.5 and the pH of your runoff is 7.0. The difference is +0.5, so using the above equation:
Soil pH = 7.0 + 0.5*
Soil pH = 7.5

If your starting pH is 6.5 and your runoff is 6.0, your difference is -0.5 and using the above equation:
Soil pH = 6.0 - 0.5
Soil pH = 5.5

 

[TonyGr]

@Rev. Green Genes I will run this test next time I water in a couple of days. I did it wrong...

Though I noticed some red color around. Especially under problematic leaves and leaf petioles. Maybe phosphorus deficiency? (https://howtogrowmarijuana.com/nutrient-deficiency/) Or it's normal for Blue Cheese strain? (https://www.google.gr/search?safe=o...0i30i19k1j0i8i30i19k1j0i30i19k1.0.KBUebhma3Ws)

First time I grow Blue Cheese.. I am so confused :S

 

[Waira]

Tony-- Blue Chz. usually develops purple colors, coming from the Blueberry side of the family,... some of that burnishing on leaves though looks like mild P defc. (pic 5, 6); lower leaves wasting away as well, but need a better pic of them to be sure,... purple petioles (leaf stem) are also a co-symptom,... the wild mixing of nutes does not help with this, organic, synthetic,.. hard to assess what NPK, secondary and micronutes are going in there,... I agree with with Rev', it's more than one thing happening, with the overall color fade as well,....
.... which brings us to pH in the pot! ...yes, the soil has some buffering capacity, but not total by any means,.. too many other influencing factors in the pot! And knowing what that in-pot pH is is key to fixing this,... is it a simple lack of type defc., or a pH lockout?... or toxicity? If you try to add more nutes to an off pH pot, matters will worsen, not improve,... Since you don't have a soil pH probe--> hsoil:... you'll have to do the run-off test, which is still not very good,... measuring straight run-off is not going to give accurate results, hence this pain in the ass test protocol,.... we can do a very crude test with run-off, using plain water, just to give us a general idea about the pH in there,.. if it's testing at say, 5.1, even if it's inaccurate, we know it's badly off pH, acidic, and we'll need to get the pH up first,... Oh, wait, you did do a run-off test, and got 7.2? Was that with plain water only, and did you pH adjust it? Odd that it's alkaline,...... what's the tap water like? Is it very hard (high mineral content?) pH?... what ratio blending with rain water? generally, it's best to avoid flushing unless it's critical,....