Reddish spots! What the hell?

[kertesz]

I've never seen a leaf like this! Do you know what is this?

How long has this problem been going on? for 2 weeks
What STRAIN are you growing? Ak-47
What was the establishing technique? (seed or clone?) clone
What is the age of your plants? 10 weeks
How long have they been in the soil mixture they are in now? 8 weeks
How Tall are the plants? 40 cm
What PHASE (seedling, vegetative or flower) are the plants in? flower
What Technique are you using? (SOG, SCROG etc) scrog
What size pots are you using? (Include how many subjects to pot) 20 litres
What substrate/medium are you using? What brand of soil mixture are you using?(percentage of perlite, vermiculite...etc?) compo sana
What Nutrient's are you using? canna terra
How much of each nutrient are you using with how much water? 30 ml to 5 litres
How often are you feeding? with every watering
If flowering, when did you switch over to using Bloom nutrients? after the first flowers appeared
What order are you mixing your nutrients? (example: veg nutes 1st, bloom 2nd ect) I'm only using one nute
What is the TDS/EC/PPM of your nutrients used? EC 1,8
What is the pH of the "RUN-OFF"? 6,2
What method of pH test was administered? Using Strips? pH pen? pH pen
How often are you watering? approx. twice a week
When was your last feeding and how often are you feeding? with every watering
What size bulb are you using? 600 watt sylvania
What is the distance to the canopy? 40 cm
What is your RH Factor? (Relative Humidity) 60 %
What is the canopy temperature? 24
What is the Day/Night Temp? (Include fluctuation range) 24/17°C
What is the current Air Flow? (cfm etc.)
Tell us about your ventilation, intake exhaust and when its running and not running ? alwalys running
Is the fan blowing directly at plants? yes
Is the grow substrate constantly wet or moist? no
Is your water HARD or SOFT? hard
What water are you using? Reverse Osmosis (RO)? Tap? Bottled? Well water? Distilled? Mineral Water? tap
Are you using water from a water softener? no
Has plant been recently pruned, cloned or pinched? no
Have any pest chemicals been used? If so what and when? no
Are plant's infected with pest's? no

 

[Peksman]

Calcium deficiency

 

[kertesz]

Jorge Cervantes - Marijuana Horticulture:

" Calcium deficiency start with weak stems, very dark green foliage, and exceptionally slow growth. Young leaves are affected, and they show the signs first."

None of them occured, and it started at the middle. Anything else?

 

[hazy]

regardless of what 'Jorge' says, calcium is a mobile element and will move from leaves to be used where it's needed. So new growth will pull from other more mature leaves for the calcium they need. If the soil is deficient . Lowering pH in your medium will cause cal and mag deficiencies.
try giving them some cal mag

how are you checking your runoff?
You really need to let it sit after watering for an hour, then add a bit more water and test that runoff.

 

[kertesz]

Thanks for the reply hazy! I'm usually cheking the water that runs off immediately after watering, but I'll do it in a way you mentioned. I'll raise the pH first, hope they'll getting better soon. What kind of pH level do you recommend, in runoff water on soil?