What causes this rusting?

[Mr Bee]

Nope, it’s about 75f and the fan in there is on low and not pointed at this. I had it before in a plant and it continued to get worse and that one had a hollow main stem assuming from lack of cal mag

Actually hollow stems is pretty common.at one point some growers were saying plants that have hollow stems produce higher quality weed.i,v seen no real evidence to back this.

 

[Aqua Man]

I also have a hard time believing they are underfed as that leaf looks like its a bit over fed. With the limited info and pics my GUESS is PH or nutrient lockout.

 

[Naturalx]

Here are some whole plant photos and other shots. Best I could get for where it was.

 

[Beachwalker]

First impression is calcium issue

 

[Naturalx]

First impression is calcium issue

Best to up the calmag in the feed? Or just foliar spray?

 

[Aqua Man]

There is more than one issue here. I would start by giving info on all of your parameters also feeding schedule and equipment.

I don't think this is a simple add cal-mag or anything kind of fix

 

[Naturalx]

There is more than one issue here. I would start by giving info on all of your parameters also feeding schedule and equipment.

I don't think this is a simple add cal-mag or anything kind of fix

Right now they're under 2 600w viparspectra LED so about 600w actual draw. Coco with perlite in 5gallon plastic pots. Fed every 2 days, 5ml GH Micro 5ml Calmag and 10ml Bloom + 20ml terpinator / Gallon of water. Water is not reverse osmosis and not bubbled. Just sits out for 24+ hours to gas off chlorine. Some plants are affected, others are not. No foliar spray, low temperatures.

 

[Aqua Man]

What's the ph and ppm of your water? Do you have fans on them? Are they in a tent? Do you have ventilation?

I have not grown in coco but have you ever flushed? Possibly salt build up causing lockout?

I'm not gonna give advice on this cause I'm not familiar with coco but ph, salt buildup are things I would look at and I agree it looks like calcium deficiency but why I cannot say. I know coco can be a pita for calcium.

It's looks like they were overfed at some point so I may start with a flush thinking salt buildup but wait for someone who grows in coco to give you advice before taking my uneducated guesses

 

[Naturalx]

I think what is slowly leading into the deficiency is I might not be upping my PH fast enough and the calcium could just not be getting absorbed. Reading the pH should be 6.2 minimum. I'll be watering around 6.5 from now on and add a bit more for the plants affected and maybe add a light foliar spray to the affected growth.

What's the ph and ppm of your water? Do you have fans on them? Are they in a tent? Do you have ventilation?

I have not grown in coco but have you ever flushed? Possibly salt build up causing lockout?

I'm not gonna give advice on this cause I'm not familiar with coco but ph, salt buildup are things I would look at and I agree it looks like calcium deficiency but why I cannot say. I know coco can be a pita for calcium.

It's looks like they were overfed at some point so I may start with a flush thinking salt buildup but wait for someone who grows in coco to give you advice before taking my uneducated guesses

Found this page and it looks like exactly what I have going on.

How to fix Cannabis Calcium Deficiency (Ca) Pics & Symptoms

Calcium deficiencies cause tiny brown spots that appear on new and middle growth. Learn how to fix this problem for good!

www.growweedeasy.com

They are in a tent, has a 6" carbon exhaust, a big fan inside on low though, it's not blowing on these affected plants directly either.

 

[Beachwalker]

There is more than one issue here. I would start by giving info on all of your parameters also feeding schedule and equipment.

I don't think this is a simple add cal-mag or anything kind of fix

^ I agree, need more info and I'd like to see a clearer picture of one of those leaf spots to rule out a fungal infection

 

[Naturalx]

I’m chalking this up to my ph pen. It kept reading high so I opened up my new one calibrated it, and haven’t had to add ph down at all so far.

I was definitely mixing things to be too acidic. While it appears to have helped these autos frost up I am looking forward to seeing how these girls handle the feed now.

 

[Cannabizz]

Hey bro,

Try a little calcium - magnesium supplement; In addition to checking out the other responses.

 

[CannabisJack]

Hey,

So my one autoflower is very slowly flowering compared to the rest but is developing some serious rusting on the leaves.

I’m about to feed them. Curious what could be causing this?

What’s your PH? And what’s the PH of your soil?