Rust spots and a tricky question: Lots of pictures and info

[farnorth]

Hey everyone.
Had a very Interesting issue arise quite literally over night and in rather severe fashion. I have several theories and have done a very healthy amount of reading to try and decide but would not mind some other opinions or better yet definite answers through experience.
I have been growing for several years and have never experienced this particular problem. Which is confusing as trying to pin down the culprit almost every bit of information contradicts each other.
This is a weird one!

environment
6 1000w lights currently alternation between 3 at 750w and 3 at 1000w every other day.
Co2 enriched at 1500. But on a timer where maintains around 900-1100
Lights are 24-38" away from tops.
Totally sealed with mini split a/c
Extra dehumidifier to help with night rh

Temps day time- 75-81
Temps night time65-71
Rh% max-64% lights on min-35% lights out

plants
Vegged 20 days from clone on day 21 today of flower.
Strains are night terror og and deadhead OG
Not effecting every plant. 12-14 of 24.

nutrients
Advanced nutrients ph perfect sensi line. The entire grandmaster line
Feeding at 60% full strength.
Medium is coco loco coco coir in 3 gal smart pots
Runoff comes out at 5.8-5.9 but shouldn't matter with ph perfect anyway. Ph goes in at 5.8 with a ppm of 1100.

Here is the issues at hand.

rust/gold spots in between veins starting in the middle of the leaf and spread outward. Main damage is in fan leaves but some new growth is effected. The leaves on the night terror are smaller and thinner and overall plant is pale. Also the weirdest part of the entire thing is how fast it happened. Within 36 hours.

Location on plant: upper 25%nof the plant. The worst is the second highest set of fan leaves with new growth barely beginning to show. The bottom of the plant and the shorter tops that are slightly hidden being perfectly healthy.
On the leaf the issues start in the middle of each blade and not on the tips or base of the leaf, just right in the middle and not on the edges though.

One plant next to another completely healthy plant

Texture: not crispy at all. Still soft. NOT brittle.

Color and shape: rust/gold. Symmetrical spotting between veins.

Anyway any opinions would be greatly appreciated...

 

[Antics]

Well it sounds like you have a lot more experience than I do, so I'll try to offer some advice until some more experienced growers can reply.

From the two topics I've known of for plant problems:
Plant abuse chart
Cannabis Plant and Pest Problem Solver

The fact that it's occurring on newer growth, and not old growth my guesses would be:
1. Light burn. How close are the lights? What about your grow room walls, ceiling, etc.. what are you using for a reflector on the walls? What about on the light? Something might be creating hotspots on the upper foliage. You can try switching the problem plants with other plants and see what happens. Raise the light/lower the plants. Check temps on the leaves with a laser thermometer and compare to temps on surrounding foliage of healthy plants.

2. One or more nutrient deficiencies. It seems to resemble symptoms associated with the following deficiencies: Boron, Phosphorous, Potassium, and Molybdenum

Remember the fact that even if all the seeds are from the same mother, you'll have different genotypes within those seeds. One plant may tolerate heat more than another. One plant may tolerate higher levels of nutes than another.
And even if you're working with clones, who all have identical DNA, the human element comes into play, and we can easily, and unknowingly create different environments for 2 identical clones.

 

[PeytonManning]

Looks like it could be cal/mag deficiency, or a ph problem

I'm betting on ph

 

[Magik1369]

I'm not convinced this is either Cal Mag or ph. I have had this issue 3 times...it always happens within 24 or fewer hours. I looked at my grow before lights out at 12 midnight. Went back into the grown at 1:00pm the next day and this problem throughout 75% of my plants. Starts at bottom but rapidly spreads even to new growth. Ph is 6.7-6.8 in soil. There doesn't seem to be any good info out there on this issue and if anyone knows, please let me know. All 3 times it has happened has been during lights out. I flushed all plants, gave em some light kelp nutes and the problem clears up. Would still love to understand the root cause.

 

[WillGrow510]

Are you using microbes in your soli. pH may be high. 6.7-6.8 in coco? I was screwed wiht pH perfect. Started using regular nutes and pH like normal and my plants started blowing up. I pH at 5.8 in coco and its great.

To be honest this looks like light burn to me. You got a lot of horsepower there. 3000 watts? How big is your room????

My bet is ph nute lock out or light burn.

 

[Munchiethefarmcat]

I think it is from certain plants drying out. Some plants need more love than others. I like to pick up every pot and feel what it needs.

 

[013]

Hi Munchie - Welcome to 420! This is an old post from 2014 - those peeps have moved on. So what’s in your garden? Drop a journal and join in.