Brown dots and patches: please help

[Kosbrand]

Problem: here and there some leaves are starting to have some small brownish dots and some others have brown patches, been pretty pale green and drooping a lot of the time
-Medium/grow method: organic light soil
-Feed and supplements used: plagron algae grow (3/4th) and power roots (1/3rd)
-Water source: tap 24h
-Strain and age
29 days old royal cheese and fast eddy
-Climate: 19 to 27 °C
- Light used: 400w hps
-Additional info:
first grow had some problems with either over or underwatering in first weeks, plants were drooping a lot of the time (which got better with upping the nutes a bit) and, ph measurement points towards slightly alkaline soil (7-7.5), new ph meter arriving shortly

I have been looking around and closest things popping to mind are calcium deficiency, phosphorus deficiency or root rot?

 

[Arthur]

You need the meter, am betting your seeing lock out due to a shift in pH. Won't matter how much of the right thing you give her, if the root zone pH is out of whack, she can't get to it.
Hopefully it will arrive soon, you need to slurry test.

 

[BBoomer]

Could be ph related, kinda looks like the start of mag def.

 

[Kosbrand]

Bluelab soil ph pen arrived. The soil Ph is around 6.1 - 6.2.

I am also pretty sure now that the last few feedings I gave were quite acidic around 5.0. So they might have shocked coming down in ph?

I fed them with 6.9 now and the soil is precisely 6.5.

The most damaged plant has Also been drooping the last day.

More insights?






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[Waira]

Kos', did you get a pH meter, or soil probe? How did you take the in-pot pH? The latter is for liquids only, but they do make a nice soil pH probe,.. basically a modified pH pen, still uses an electrode bulb and all the care that entails,....
I agree, the soil was likely too acidic which locks out P,.... Plagron is pretty mild, right? What are the NPK#'s? I do see a bit of tip burn, but that's a fairly generic symptom, not always nute burn,... Symptoms do look like P defc. mainly to me too...
Drooping could be a few things; get me whole plant pics please.... Any sort of over- or under-watering recently? Are the drooping on a daily cycle, starting just before lights out? (that's something else, a normal physiological response)...

 

[Kosbrand]

Kos', did you get a pH meter, or soil probe? How did you take the in-pot pH? The latter is for liquids only, but they do make a nice soil pH probe,.. basically a modified pH pen, still uses an electrode bulb and all the care that entails,....
I agree, the soil was likely too acidic which locks out P,.... Plagron is pretty mild, right? What are the NPK#'s? I do see a bit of tip burn, but that's a fairly generic symptom, not always nute burn,... Symptoms do look like P defc. mainly to me too...
Drooping could be a few things; get me whole plant pics please.... Any sort of over- or under-watering recently? Are the drooping on a daily cycle, starting just before lights out? (that's something else, a normal physiological response)...

Thanks for your reply.

They recovered from the drooping and I dont think more leaves got damaged. Do leaves repair from those brown dots? Im guessing not.

What I did is upped the watering and nuting a bit (4 2 4 alga grow) to plagron suggested amount.

I also added quite some powdered sea lime (maerl). Don't know if that did the trick.

Another question: I now increased the hps from 400 to 600W. The temperatures rise to 31C. Is that too much and is it beter to stay at 400 with 27C then?

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[Kosbrand]

I use the bluelab soil ph pen. It can be used to measure liquids and soils. Very easy to use..

Therefore I am certain now that my soil is between 6.3 and 6.5. The feed I gave them when using my faulty ph pen was pretty acidic (5.0 to 5.5). That might have shocked them and choked out some nitrogen and calcium. Now ever feed is between 6.2 and 6.8.

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[Waira]

good on the pH!
... nope, dead tissue is dead tissue,....
... 31C is high, too high likely,... much of this depends on your RH%, so critical,... have you read up on vapor pressure deficit (VPD)? ...check out the Reference section for a good article on this, which discusses how T and RH% affect transpiration rates from leaves,.. this is the key to proper flow of both water and nutes from root to tips! If T and RH% are out of balance, the whole machine struggles and problem snowball from there,...
...watch that in-pot pH carefully now that the lime went in,.. top dressed, or watered in? Is it basically pure CaCO3?
... with the pH and feeds corrected, it'll take a few days to tell for sure if progression of symptoms is halting,....

 

[Kosbrand]

It was maerl, some kind of natural sea calcium. Did add quite a lot.

Ph of soil is 6.6 now.

It has grown okay but it is getting more yellow fingertips with necrosis between leaf veins. What is this, deficiency, burn, heat?

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[Waira]

looking like P defc. to me,.....pH is good, so get the PK boosters going, or more bloom nutes....