[Douglas.Curtis]

When I go below 67F in hydro, I have the same uptake problem.

[Michael49]

Originally Posted by OldBeans

Yes, it's very low, I've found strains with blueberry genetics in them are the most sensitive to lights off temps. Ideally 20c/68f is the minimum temperature for lights off imo

If you can't warm the intake, can you insulate the pots with bubble wrap? Or slow your extraction down for lights off??

I used to feed the outtake from my veg tent into my flower tent and that always worked for me.

I don't think giving more food will make a difference with lights off temps so low, the root all will be a few degrees colder than ambient temps

Good luck friend!

Thanks for the input - I will try to increase the nighttime temps.

[Michael49]

I watered today. 1 1/2 tsp/gallon of Organic Roots Buddha Grow (thought they might need a little nitrogen) plus 5ml/gallon of CalMag. I'm trying my best to raise the nighttime temps.

Here's a photo of several dying leaves that I removed to see if this helps ID the problem and updated photos of the girls.....

[Michael49]

Forgot to mention that I recalibrated my pH meter last night and it was reading high!! So when I thought I was pHing my water to 6.5 it was probably more like 7.5!!!

[slownickel]

Sure looks like a phosphorus deficiency...

[Ready4]

Your problem looks like it has gone away, your newer growth is healthy and green.
Those older damaged leaves all need to be removed, once in that condition they will never improve and just take away energy from the plant. When you cut away all those crappy leaves, your plants will look just fine. Don't overfert and add a little calmag in a couple weeks from now.

[slownickel]

I would suggest a light phosphorus feed, say 0.5% phosphoric acid. Do it light on one side of a plant, on one branch. That is how you learn.

[slownickel]

The give away on a P deficiency on this leaf is the fact that the strong chlorosis does not obey the veins. Phosphorus is the only element that will do this. Most everything is margins, interveinal, etc. I would also bet you would see a big response to some micronutrients like Mn for example. Again, do one branch and watch what happens.

A good one to confirm positive response is to test petioles, after washing of course, with a refractometer. If the plant got a response, the brix will increase, in about 24 hours or so.

Also, if the P response shows up, that branch will start praying heavy.

Experiment my friends!

[PDX Dopesmoker]

Originally Posted by Douglas.Curtis

When I go below 67F in hydro, I have the same uptake problem.

Thats pretty much the same number I've noticed for soil temperatures. Once if goes into the mid-lower 60s things seem to start shutting down pretty quickly. Sitting right at the edge of disaster in the upper 60s seems to be where the flavor is at.

[geneva_sativa]

Something I found with a closed room at night is that high humidity during lights out can make temps stay much lower than they should be.

I remember a case when night temps in a closed room would always be 5-8 degrees colder than rest of rooms in house. . . put a dehumidifier in during lights out, and viola, temps jumped up above 70 degrees.