Calcium deficiency and light/heat stress?

[NHWhites]

Flowering under a HLG qb260. These are known to require more calcium uptake, which is why I’m leaning towards a calcium deficiency. Thoughts?

 

[az2000]

Flowering under a HLG qb260. These are known to require more calcium uptake, which is why I’m leaning towards a calcium deficiency. Thoughts?

At that stage of the grow, I automatically think salt build up and nutrient lockout. (It doesn't look as spotted/rusted as Ca def.).

If you're growing in soil, what kind of soil and nutrients, supplments? How much do you feed? How much runoff do you typically have? Can you measure the PPM of the runoff?

I'd like to see photos of the entire plant(s), under normal lighting.

 

[NHWhites]

At that stage of the grow, I automatically think salt build up and nutrient lockout. (It doesn't look as spotted/rusted as Ca def.).

If you're growing in soil, what kind of soil and nutrients, supplments? How much do you feed? How much runoff do you typically have? Can you measure the PPM of the runoff?

I'd like to see photos of the entire plant(s), under normal lighting.

I’m growing in soil, Michigan M3. I haven’t really fed much other than URB Natural and aloe. I use straight tap that I let sit out to de-gas and I don’t check ph. I have minimal runoff as the plants are in smart pots. It’s the plant in the top right corner

 

[az2000]

So, it's a complete/composted soil? It supplied all the nutrients through the grow? Since you're not feeding it anything, I guess salt buildup/lockout is ruled out. I'd say it's hungry. Maybe the soil didn't have enough nutrients for this length of growing(?). But, do you have any nute burn in the tips/edges? Do I see that in the 2nd photo from the top? That makes me hesitant to say it should be fed. If that is nute burn, when did it happen?

I've never grown in a soil amended with everything it needs (which sounds like you're doing). I want to. I've read about it. I thought people feed teas at some point? Guano teas? Maybe it needs that?

 

[NHWhites]

Yeah the soil is supposed to take it all the way through but never does lol. The top burn you see is from veg and it’s ever so slight. The microbes were really pumping. I gave them a light feeding last night. QB’s are known to cause plants to require more calcium than hps or cmh bulbs. I think just need to start adding Herculean Harvest to my waterings

 

[Dirtbag]

That does not in any way look like calcium deficiency. It does look like advanced phosphorus deficiency though. Especially how the margins of the leaves look pale, and the big necrotic patches.

I'd feed it some bloom fert. Foliage wont come back, but It should stop getting worse.

 

[MIMedGrower]

I agree with @Dirtbag

But I would use a complete balanced fertilizer as the nutrients left in the soil are likely imbalanced at this point.

 

[az2000]

QB’s are known to cause plants to require more calcium than hps or cmh bulbs.

[Note: I typed this post before seeing subsequent posts advising against Ca def. I thought I'd go ahead and post it since you think Ca def could be a risk in your environment. This information might help if you ever do need to supplement Ca.]

I've often heard of (and experienced for myself) LEDs requiring more Mg. Never heard of Ca being an issue. But... if you think it needs it, you can dissolve gypsum up to 2.5g per liter of water. (Ex. 1/2 tsp of my gypsum weighs 3.5g.). (Hint: It dissolves easier in hot water.).

The question is: how much to use? I think a safe way to look at this is how much Ca is given with a typical "calmag" dose. If you had a serious deficency, 10ml/gal of Botanicare Cal-Mag+ would be resonable. Based upon that product's liquid density (the weight of 10ml volume), and it's guaranteed analysis: that should add 181ppm total to a gallon of water. If so, 89ppm are Ca (33ppm is Mg, 55ppm is N, and 3ppm are iron).[1]

So, you would want to dissolve enough gypsum to produce about 89ppm. Gypsum contains 23% Ca (and 19% sulfur) by weight. Therefore: 1.5g will contain 92ppm CA (and 74ppm S).

Dissolve 1.5g in a liter of hot water. Then add that to enough water to make a gallon.

You can sanity check this. Measure the ppms of your liter of water. After dissolving 1.5g (and after it cools), it should measure about 629ppm (plus whatever the ppms the water measured to begin with.). This should become ~166ppm when you dilute it into a gallon (plus, again, whatever the water's ppm is).

[1] I have a spreadsheet that figures this stuff out. Botanicare's CalMag+ has a liquid density of 8.81 lbs/gal. Then we know the guaranteed analysis. (N=2%, Mg=1.2%, Ca=3.2%, Fe=0.1%). Calculate the weight of 10ml, and you can get to the weight contributed by each element, and the ppms each creates per liter (convert to gallon dilution).