Progressive Yellow Spots on Leaves

I hate to toss out another full unit of Veg plants, but I sense disaster looming on the horizon. I have several units of 12 veg plants growing beautifully. However when I run a unit with clones from this one vendor, I get the problems shown in the pictures below. The new growth looks good, but after leaves get to full size they begin to develop yellow spots.

These spots progress until it eventually overtakes the leaves and they die over a week or 2. I've tried changing nutes, trimming off impacted growth, adding additional cal-mag, adding Bloom nutes for the addttional p/k...nothing seems to help.

I looked through the Mosaic Virus thread, but don't think that is the cause. The entire leaf will eventually die our instead of just the infected area as it appears happening with the virus.

The only things different on these plants from the rest of the healthy garden are the rockwool cube attached to the clones, and that the clones came from a source besides our center.

Any advice ?? Thanks in advance!! I would hate to pitch a second unit with this issue

The pictures: [questionnaire answered below]









HYDROPONICS:

What STRAIN are you growing? This unit is Big Bud, but I just tossed out an entire unit of MediBud clones from the same vendor.
What was the establishing technique? (Were the seed or clone?) Clones received rooted in RockWool, dropped into hydroton top drip.
What is the age of your plants? 3 weeks from rooted clone
What PHASE are the plants in? (seedling, vegetative or flower) are the plants in? Veg 24 hour 4x4' T5
What Technique are you using? Top Drip on cycle timer 1 on 5 off.
What substrate/medium are you using?(Hydroton, RockWool etc.)RockWool transplanted into hydroton.
What is the Nutrient temperature? 72f with EWC tea added.
What Nutrient's are you using? Botanicare Pro Gro, Karma, and Cal-Mag
What is the TDS/EC/PPM you are using? Running +/-850ppm
What is the pH of the "Tank"? 5.8-6.0
Are you sure your calibration is correct on your equiptment? yes using 7.0 ph cal solution on digi meter
When was your last watering? Ongoing
When was your last feeding change? (ie. grow-bloom-micro-additional) Changed res but same nutes. Additional Cal Mag. On the other unit I recently tossed I had attempted adding Pure Blend Pro Bloom suspecting a p/k deficiency.[to no avail]
What size bulb are you using? 4bulb 4' T5
What is the distance to the canopy? 12"
What is your RH Factor? Range? 70% to 50%
What is the canopy temperature? Mid 70's f
What is the Day/Night Temp? (Include flucutaion range) 68f-78f
What is the current Air Flow? (cfm etc.) large airconditioned room with good fan circulation.
Is the fan blowing directly at plants? No
Is your water HARD or SOFT? Soft
Has plant been recently pruned, cloned off of or pinched. No.
Have any pest chemicals been used? If so, What and When? No.
Are plant's infected with pest's. No.

some sort of deficency, should find a solution on here, defo no need to throw out any plants man.




peace mick.

Are you SURE about the pH? It sure looks like a pH lockout...

It looks more like a deficency to me, when I had PH problems, before I bought a pen, i would get black/rust colored spots all over the fan leaves, then the leaves would eventually dry out and die.....IMO, its not a PH issue, more like a deficency of some sort. Just my opinion.

Yeah, I've checked the PH with the digi meter and calibrated it to check as well.

I think the daughter may have figured it out, and we are already seeing results with the fix..

The rockwool blocks were the only thing different between what the clone guy was giving us and what I was running from in house cuts. I believe that the cubes are holding too much water causing a Mag Lockout. She found in the Cervantes grow book that over watering locks out the Magnesium.

We cut back the nutes to about 500 ppm, then added 2tsp per gallon of Epson Salts [Magnesium Sulfate] into the reservoir. We also added an Epson Salt foliar spray based on 2 tsp per gallon of water per the Cervantes book.

I have to say that after an overnight treatment we're already seeing an improvement. The leaves overall are greener and the plants shot up in growth and stature. I believe we are on the right track with this.

So, in the end, these are my thoughts:
The rockwool cubes are holding too much water when used with a 1on / 5 off cycle timer.
The over watering on the small veg plants is causing a Magnesium lockout.
Foliar spray of 2tsp/gal of Magnesium Sulfate [Epson Salts] with 2tsp/gallon also added to res seems to be showing improvement.

Once the plants establish their 5 gallon root structure the rockwool will no longer play into the mix.

We'll see, but I think we're on the right track.

Hope this helps somebody going forward...