Why do these leaves fall?

[elcoloan]

Why are these fan leaves from the bottom falling? The darker one in the pics is from the top of the plant, I snipped it to compare.

They are from a photo plant that is in its 3rd-5th flowering week. It's a Black DOG grown in coco hempy bucket, with Greenleaf nutrients and under a single 65w 3500k Autocob in a 2x2x4.
Temp are 16-24 C, RH is 60-74%.

She gets 1.1-1.2 EC (about 400 ppm Mc v1 + 130-160 bud explosion and 20-30 ca-mag pro).

I fertigate twice a day, with 30-50% runoff.

I suspect it's the high humidity, too much water, or a Mag def maybe due to low temps o the low Ca-Mag dosage. What would you think it is?

 

[FullAuto245]

Increase temps and cal mag a bit. The warmer air will evaporate some moisture. Some of those leaves look like magnesium deficiency and others look like maybe a P/K issue to me but get multiple opinions. It could be a simple ph adjustment to allow for more uptake of the cal mag as well.

 

[Arthur]

Lack of light would be my guess. 65 is good for a little over 2 sq feet. Plants know when leaves aren't getting enough light, and will get rid of them. I don't see anything that would have me thinking deficiency. 2x2 is 4 square feet, 2 of those lights are needed to cover. Also this is also a photo, your watts needed per square foot goes up in flower. Closer to 40 watts per sq foot.

 

[Waira]

-- I'm not sure mate, if the plant is otherwise healthy, no stress, issues etc.,... Something is kicking off the hormone response to form the abscission layer too early, usually that a reaction to something catastrophic,... low light they still may cling on, typically the plant will suck out the mobile nutes first too, then ditch it....Leaves look only partly tapped.... Any weird exposure to overripe fruit (ethylene, a ripening hormoine produced naturally BTW), chemicals, etc.?

 

[elcoloan]

.... Any weird exposure to overripe fruit (ethylene, a ripening hormoine produced naturally BTW), chemicals, etc.?

Nope. I did forget to mention i have springtails in high amounts, but other than that... tap water that has 50-80 ppms, 6-7 pH. I use white vinegar to lower pH, and baking soda to increase pH, but barely ever use the baking soda just 5-10 drops of vinegar.