Expert help needed!

I would call myself somewhere between an intermediate and an advanced grower. After a 20 year hiatus to raise children, I am back at it with the goal of a perpetual harvest.
My current system has mother plants under T5's in 5 gallon buckets of soil, a 25 site aeroponic cloner under a single 18" fluorescent plant light from Home Depot, a 2' x 2' Hydrofarm Mega Garden ebb&flow table under 24hrs of a CFL grow light which holds 16 square 5"x5"x7"h pots of Growstone and Hydroton mixed 3 to 1, respectively. The nutrients used in this 9 gallon reservoir are from Vertigro, which uses the common 2 part system (calcium nitrate and a base) which I start @ around 600ppm week 1 and have been adding some of the General Hydroponics Flora Nova Grow (that came with the Hydrofarm Mega Garden) and a dash of Superthrive at the beginning of week 2.
This has produced growth rates and amounts the likes of which has to be seen to be believed. Simply phenomenal. A 3 inch cutting rooted for 14 days in the cloner will be 10" tall, have 4 to 6 branches, and 8" fan leaves with a 16" circumference! Just ridiculous! At this point these retardedly robust beauties move to the sealed flowering room, which consists of an
8' x 4' ebb&flow table with a 100 gallon reservoir. Chiller set to 66°-68°. Mini Split AC @ 78°. Dehumidifier(which drains to the reservoir) set to 45%-50%.
Co2 enrichment via propane generator (1250-1500ppm daytime only).
All controlled via Atmospheric controller and Blue labs monitor

Two 1000w HPS in sealed hoods 12/12 regimen

Reverse Osmosis water

A flood and drain cycle takes 11 minutes and are set to repeat every other hour during the day.

The plan is to have 16 plants per rotation or "batch" and 6 batches constantly in flower.

Every batch does GREAT until about week 4, then: BAM! It starts. First the purple keaf stems, then the fan leaf blades come together, even overlap, fading between leaf veins, then total yellow but not N deficient yellow. Hard, bright yellow. Grey, crunchy necrosis on lower fan leaves.
Buds still form but not well.
I see that it's a calcium and magnesium issue and have added:
121 grams of Magnesium Sulfate (9.87%),
88 grams of Calcium Chloride (27.3%),
10 grams of iron chelate (10%)
Which has raised my ppm significantly.

I was keeping pH @ 5.8 which seemed great until this chronic issue. I adjusted down to 5.2 but saw no improvement and continuing worsening.

I'm sure I haven't supplied enough information but hopefully this is enough for you to be able to ask me.

Need help desperately. I have absolutely no other input as nobody knows about this (shhhh!)

Additional information

Additional information

I'm using General Hydroponics maxibloom @ 7.5g/gal

Heres my simple look at it. Your base nutrients more than likely have plenty of ca n mg. So you are overcompensating by adding more of them, thus throwing off your good concentration already formulated in the base nutes. Your trying to compensate for a environmental or human error problem.

I'd start with the root zone. My first thought goes to are u adding flora nova n super thrive to your recirculating res? Organics in a recirculating res are a no no for me. That might be causing some ph drift problems or root rot.
Your water temp is a bit low, but I'm not sure it would cause that severe a problem, but u might try 72f. Also is it possible they r being overwatered? The only other thing I'd do is get ur rh up to 70%, at least thru the first half of flower till u get large cola formation.

Maxibloom has more than plenty of calcium for your needs, the calcium chloride can be eliminated. It's short on Magnesium though, especially for mag hungry strains. Adding .5g/gallon when you first mix your flowering res can make a world of difference. Up to a gram/gallon is ok, remember to use just enough to take care of mag deficiencies, no more.

Your ppm's should be at a maximum of 800ppm, hopefully less. What have you been running for ppm in flower?

It's all guesses until you post a pic

Bush Dr said:

It's all guesses until you post a pic

Click to expand...

QFT

You may want to try not having your condensate water go back into your res. Overtime you don't know whats being collected on the fins which goes into your condensate water.

I used to do it but I noticed some cal/mag problems so I stopped using it and everything got better. I haven't tested to recycle that water again because I didn't want to and I may be wrong. But if you want to diagnose your problems, its one variable at a time. GL!

My guess is ph. Mag is more available in hydro at the higher end of the ph scale. Let ph drift up to 6.1 before adjusting back down to 5.8. 5.2 is way low.

I don't see any mention of how often you change out the res. Over time your fert ratio's change as the plants use more of one thing, and less of others, throwing ratio's off. I'm assuming 11 mins is for both flooding AND draining?
Also are you aerating the res? What do your roots look like?

chris harris said:

I don't see any mention of how often you change out the res. Over time your fert ratio's change as the plants use more of one thing, and less of others

Click to expand...

When you run a balanced nutrient mix, there's zero reason to dump a res. I haven't dumped a res in flower for what... 12 years now? Feed your cannabis a plate it can clean every meal.

As plants transition from veg to flower there uptake of nutes change, using more P and K, leaving more N behind in the res, causing a unbalanced ratio, which are not reflected in the EC reading.
You can do "add backs" with your modified ratios, but you are still adding to an existing unbalanced res, unless you are running a small res, where your "add backs" are equalling your total volume in the res, in a short amount of time. Which is, in essence, doing a res change.
It's still a guessing game as to knowing exactly how much of each element the plant is using daily. Throw in a multi strain, or perpetual grow, and your lost, if your basing your judgements on EC alone.
Most guys run large res, allowing for fluctuations, without reaching toxic levels, and doing changes, for the reasons above.
Keep doing what your doing if it works for you. Didn't come here to debate, or derail, was just offering some suggestions to the OP.

chris harris said:

As plants transition from veg to flower there uptake of nutes change, using more P and K, leaving more N behind in the res, causing a unbalanced ratio, which are not reflected in the EC reading.

Click to expand...

I never mentioned anything about a veg reservoir. Completely different mix.

Neither did I. The first 2 weeks of flower is a transition period. In fact, the requirements of a plant continually change during the flowering period.

chris harris said:

Neither did I. The first 2 weeks of flower is a transition period. In fact, the requirements of a plant continually change during the flowering period.

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Not enough to require significant adjustment, or change out.

SUCCESS!
I switched to 7ml/gal General Hydroponics Flora Nova Bloom and 3ml/gal Botanicare Cal-mag Plus with weekly reservoir change and have eliminated the problem completely!
I have not had to adjust the pH whatsoever and everything is within ideal parameters.
If you come to this forum seeking a solution to Cal-mag problems do yourself a huge favor, do not try to DIY your nutrients. I tried. It sucked! I called Advanced Nutrients customer service and they were amazingly helpful. The "expert" with whom I spoke was quite familiar with my plight and recommended this solution! Epsom salts and Calcium nitrate (nor calcium chloride) ARE NOT THE SAME!
Maxibloom will also work just fine ALONG WITH the Cal-mag Plus if you are using RO water.

Good luck everyone and thanks to all who posted replies!

FWIW, I wouldn't ever trust a word that came out of an AN rep. I've been told by many wise ol' men that epsom salt is viable source of magnesium, and I'm more infinitely more inclined to believe them than some snake oil salesman. I do use gh's calmag, but mainly during early veg. My clones love that shit.

Dirt Bag said:

SUCCESS!
I switched to 7ml/gal General Hydroponics Flora Nova Bloom and 3ml/gal Botanicare Cal-mag Plus with weekly reservoir change and have eliminated the problem completely!
I have not had to adjust the pH whatsoever and everything is within ideal parameters.
If you come to this forum seeking a solution to Cal-mag problems do yourself a huge favor, do not try to DIY your nutrients. I tried. It sucked! I called Advanced Nutrients customer service and they were amazingly helpful. The "expert" with whom I spoke was quite familiar with my plight and recommended this solution! Epsom salts and Calcium nitrate (nor calcium chloride) ARE NOT THE SAME!
Maxibloom will also work just fine ALONG WITH the Cal-mag Plus if you are using RO water.

Good luck everyone and thanks to all who posted replies!

Click to expand...

FloraNova Bloom is something I personally used for a few years as a base nutrient mix. It works perfectly well with epsom, when you mix and tend the reservoir correctly( No changeouts). I quit using it when I got tired of the shaking and the dirt sediment.

your ph should be closer to 6.5 by week 4 flower, low ph causes nutrient lockout