Phosphorus deficiency?

[nomoresnow]

Just finished 8th week of 12/12, growing in coco/perlite and have been using GH flora trio and calmag for the entire grow. I have been off the gro formula for a while now and currently feeding 5ml per gal of bloom, 2.5ml per gal micro and 2.5ml per gal calmag. Feed every day with a good amount of runoff. I had been slowly reducing the amount of micro but the leaves were getting pale so I raised it back up to the current level. Temps are high 60s night and mid 70s day with 35% rh.
I should also add that I use ro water and ph to 5.8-6.0 and ppm lately has been around 370.

I believe the plants are very close to harvest, 70/30 milky/clear trichs but no amber yet.

From pictures I've looked at it looks like phosphorus deficiency but not sure. Any thoughts?

 

[Ralei]

It is phosporus def for me too.

 

[tropicalcannabispatient]

Hope this helps

 

[nomoresnow]

Hope this helps

Those are the charts that led me to think phosphorus deficiency, now I just have to figure out why. Too little nutes, too much, some kind of lock out, natural progression of plants at this stage?
It could also be a Potassium problem by looking at the charts.

 

[Dr.Pecker]

Phosphorus deficiency is normally accompanied by purple stems. Too much potassium can lock out calmag. What's the growing medium? Your ph range is for hydro.

 

[nomoresnow]

Phosphorus deficiency is normally accompanied by purple stems. Too much potassium can lock out calmag. What's the growing medium? Your ph range is for hydro.

They are in coco/perlite about 70/30. Some of my older leaves near the tops of the plant have purpleish stems.

 

[nomoresnow]

I fed them very light nutes the last 2 days and extra water. Yesterday the ppm going in was 110 but ppm of runoff averaged 300 between the 4 plants. I never check runoff so not sure what to expect but that seems high to me so maybe there is salt buildup or something similar going on. I will try the extra water with low nutes a couple more days and see what happens. Also checked ph but that was 5.9 in and 5.3 out so I think that is OK.

 

[Dr.Pecker]

I fed them very light nutes the last 2 days and extra water. Yesterday the ppm going in was 110 but ppm of runoff averaged 300 between the 4 plants. I never check runoff so not sure what to expect but that seems high to me so maybe there is salt buildup or something similar going on. I will try the extra water with low nutes a couple more days and see what happens. Also checked ph but that was 5.9 in and 5.3 out so I think that is OK.

Ph is dropping out for some reason. 5.3 is way low. How do your roots look?

 

[outlier]

First pic looks like a mg deficiency. I'd flush with some calmag and 1/2 dose of nutes mate until your runoff ph and ppm are the same as what's going in. Agree with Dr that your runoff ph is too low. That may be causing lockout.

 

[nomoresnow]

Ph is dropping out for some reason. 5.3 is way low. How do your roots look?

First pic looks like a mg deficiency. I'd flush with some calmag and 1/2 dose of nutes mate until your runoff ph and ppm are the same as what's going in. Agree with Dr that your runoff ph is too low. That may be causing lockout.

I watered them heavily with 1/4 strength nutes 3 times today, second watering Ph in was 5.92, runoff was 5.3 - 5.4. Last watering I ph'd to 6.5 but didn't measure the runoff yet.
My roots poke out a lot near the bottoms of the smart pots and the coco mix has been very dense with roots most of the grow with a lot of roots on the top of the pots just under the loose perlite. Color wise the ones on top are kind of a bone color but those are all I can see without pulling them out of the pot.

For what it's worth, most of the damaged leaves are right under the light and create a light green rectangle in the whole canopy. The leaves at the edges of the room all look much better, maybe the ones closest to the light work more/harder so they run out of food first.

 

[Dr.Pecker]

Could be a few things. The spots could be water spots, at night they sweat then the light comes on and burns the plant. Do your fans run when the lights are out? If not they should be. When you harvest roll the smartpots down and look at the roots, make sure they aren't rotting. Roots should be nice and white not dry or brown. It could be a over watering issue. Decaying roots will drop the ph and start showing deficiency. The square light spot could be bleaching because they're too close to the light.

 

[420PyRoS]

http://www.growweedeasy.com/phosphorus-deficiency-cannabis I just went through phos deficiency. Yours does resemble it a bit. Biggest signs for me were stems on fan leaves (only fan leaves) started turning pink --> red ---> Purple over 2 days and leaves were constantly drooping. The bud sites are still green stems, but all the fan stems are purple. My assumption is the fan leaves protected the rest of the plant. And that damn dreaded droop like it was always overwatered/underwatered