Does this look like a phosphorus deficiency? Slight reddish spots on lower leaves

[roperman]

I've got four plants in a 4 x 4 tent, almost two weeks into flower. One of the plants has some lower leaves turning slightly yellow, with reddish spots. The other three plants look ok. pH has been between 5.9 and 6.0.

Calcium deficiency is supposed to hit the top leaves first and go down. My top leaves are fine, just the lower ones, so that tells me maybe phosphorus deficiency. I've been looking through other photos of sick leaves and I don't see a perfect match to what I have.

This is a hydro setup in coco, watering once a day for 10 minutes, drains back in a reservoir, all four plants get the same nutes at the same time. I'm using 1/4 strength nutes from the GWE guidelines for coco grow. I am using calmag. ppm's are around 470 to 500. I've been foliar spraying daily with a full strength calmag (diluted 1 teaspoon per gallon) when the lights are off in an effort to stave off calcium deficiency.

Maybe I'm low on the ppm's - I've read that in flower you can go up to 1000 but I've been hesitant to do that because my plants aren't lowering the ppm's much between reservoir changes (once a week).

I'm stumped, any ideas would be greatly appreciated!

[FlyingDutchPaddy]

Hi Roperman,

https://www.growweedeasy.com/wp-content/uploads/2010/10/cannabis-calcium-deficiency-bottom-plant-lack-of-light.jpg

i think it could be calcium deficiency...

https://www.growweedeasy.com/calcium-deficiency-cannabis

P might be possible, but i'm leaning towards calcium as the leaf stems look alright, not too reddish in color.

thats my guess.

good growing!

[9fingerleafs]

gotta agree with paddy here, looks like the culprit is calcium, the plant looks a bit light so i think you could really use some calmag

[Ballisticsuk]

Is this led lights

[SoOrbudgal]

Ballisticsuk you are way late making comments on this post it's over 3yrs old, where do folks get these old post?

[9fingerleafs]

I think just thru Google search SoOrbudgal

[Ballisticsuk]

Aah sorry my bad I see it is led
What's the ppfd at the canopy
Are you running your extraction full pelt
What is your background water ec or ppm
Leds change the way the plant uses calcium if you run your room like an hps room but with leds you get nute probs
You want to extract the bear minimum move your lights up 24 inches at start of flower and gradually move them down to meet the stretch

It took me a long time and many deficiencys to work out the environment makes the biggest difference the other thing is coco if you don't buffer it correctly at the start then it leaches calcium from the resovouir which makes it appear the ec drops so more is added and you get calcium lock out but usually magnesium will rear it's ugly head with it

[Ballisticsuk]

Still gives some info for those that discover it I've learnt a lot from new posts on dead threads lol

[OldManGrower]

If you were in soil, I would say your PH is too low. I do not grow in coco but it sure looks like a PH issue to me.