Cal deficiency but feeding cal/mag ? Leaf pics

Hello all, please find pics of leaf, I suspect it is Calcium deficiency which I just don't get. All advice greatly appreciated.

It isn't every leaf on every plant maybe 5%. with some worse than others. The plants are 4 weeks into 12/12 tomorrow.
Growing top feed Rockwool croutons in 20 litre pots which are full of roots and have a secondary root system growing into the water below, 5" gap between pot and solution. Roots are fantastically healthy.

Feeding GH 3 series (soft water), Grow, Micro, Bloom. 3-2-1 in veg, 1-1-1 transition, 1-2-3 after stretch. Cal Mag at half dose, Silic Acid at full dose until stretch has finished also beneficial's

0.9 ec veg, building up to 1.2-1,3 max in flower then decreasing near the end. At the moment these plants are on 1.2 ec. PH 5.7 - 6.0.

General Hydroponics suggest NOT feeding cal/mag with their soft water version but as I feed quite low thought half strength would suffice. My background tap water is soft 0.2 ec.

Plants had a hard defoliation at 3 weeks and did not show any stress although bud formation seems to have slowed slightly but I always get a bit panicky around 4 weeks so may just be my imagination as otherwise the look healyhy, maybe a bit to deep of a green if anything but showing no signs of nute burn on tips.

Are you sure your pH meter is correct?

Yea sure mate it's an Aphera and calibrated regular.

LEDs? Temp and humidity?

fartoblue said:

Feeding GH 3 series (soft water), Grow, Micro, Bloom. 3-2-1 in veg, 1-1-1 transition, 1-2-3 after stretch

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Try Lucas Formula. 1:2 Micro to Bloom (no Grow). Shouldn't need cal/mg even with RO. I thought 4:8 ended up in my preferred EC range.

You mentioned cal-mag at half dose, is that 2-3 ml/gal? If so, bumping to 4-5 ml/gal may help.

Things seem to be getting worse (see pics). Some of the leaves near the top are drying up going brittle and dry , almost dead, and more leaves are affected.

It is mainly on the upper leaves. I flushed them out and added a new tank at 1.1 ec 5.8 ph. I am getting ph drop but thought this was normal at 3-4 weeks.

600 HPS at 18" from bulb to plant, temps 23 on, 19 off, humidity in 40's. I have had this problem before at this time in flower so I must be doing something wrong.

I have today increased the ec to 1.2 and increased the ph to 6.3, I am correct in thinking calcium is best taken with the PH over 6 in RDWC.

Could it possibly be nute burn even at such a low EC ? There is no browning of the leaf tips.

The roots are pearly white on every plant, but as mentioned I do get PH drop almost daily.

SheeshM said:

You mentioned cal-mag at half dose, is that 2-3 ml/gal? If so, bumping to 4-5 ml/gal may help.

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Yes mate I am feeding at just over half recommended dose of Botanicare cal/mag but I feed GH 3 part soft water and they recon I don't even need to supplement cal/mag. My background tap water is 0.2ec.

In my opinion you have a nutrient lock out due to ph (a real hot decomposition of nutrient over feed at some point or built up) that's what's furthering your cal/mag def I'd flush your medium ph the run off I'd make sure you get a nice clean run off then start fresh with a nice soft/low nutrient feed Ppm meter will help you find out how hot your nutrients are going into your medium, Ive seen this when I first added molasses (far too much) to a grow I did in coco coir it bonded to the medium and was a prick to flush out, I've always consistently added 1ml/per litre of cal/mag to my nutrients and 99% of all my garden veges and other plants alike keeps them nice and green in 10years of growing I havnt had a issue adding cal/mag, but nutrient lock out is a painful crop destroyer that if not addressed quick enough will ruin any chances of getting nice buds, question tho what kind of medium are you running? Or are you doing dwc, I'm a coco or soil based grower best of luck bro

any chance you got bugs? have you looked at the underside of the leaves with a scope for mites?

Sm4shMAN said:

In my opinion you have a nutrient lock out due to ph

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i think its some type of lockout too but he says his meter is correct. if it's anywhere in high 5 to low 6, there shouldn't be a problem

Week 4, Bluish ting. Gotta vote Phosphorus. Reset with a flush and move on?

What are your lower tank numbers doing?

rkymtnman said:

i think its some type of lockout too but he says his meter is correct. if it's anywhere in high 5 to low 6, there shouldn't be a problem

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Just been out and checked it was reading 7.1 in the 7 solution and 4.1 in the 4 solution. PH has never been lower than 5.5 or higher than 6.2.

This has me beat . The ec did creep up to 1.3 at around 3.5 weeks in and this is when it started.

No bugs either I have scoped the leaves.

Sm4shMAN said:

In my opinion you have a nutrient lock out due to ph (a real hot decomposition of nutrient over feed at some point or built up) that's what's furthering your cal/mag def I'd flush your medium ph the run off I'd make sure you get a nice clean run off then start fresh with a nice soft/low nutrient feed Ppm meter will help you find out how hot your nutrients are going into your medium, Ive seen this when I first added molasses (far too much) to a grow I did in coco coir it bonded to the medium and was a prick to flush out, I've always consistently added 1ml/per litre of cal/mag to my nutrients and 99% of all my garden veges and other plants alike keeps them nice and green in 10years of growing I havnt had a issue adding cal/mag, but nutrient lock out is a painful crop destroyer that if not addressed quick enough will ruin any chances of getting nice buds, question tho what kind of medium are you running? Or are you doing dwc, I'm a coco or soil based grower best of luck bro

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I am in a hybrid RDWC rockwool mini croutons but I did have this problem in pure RDWC. I am doing something wrong at about 3 weeks into 12/12 and don't know what. I feed GH series at 1-1-1 for the first 2-3 weeks after flip then 1-2-3 (GMB)

Jypsy Dog said:

What are your lower tank numbers doing?
View attachment 4414406

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It has been ph falling, ec static, water level falling.

fartoblue said:

then 1-2-3 (GMB)

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i still think you should try Lucas formula for a week and see what happens.
1:2 micro to bloom. 5mL /10mL should put you close to 1.2 EC. if not, 4/8.

Jypsy Dog said:

Week 4, Bluish ting. Gotta vote Phosphorus. Reset with a flush and move on?
View attachment 4414405

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I did look at this earlier in the evening but can't think why I would get a P deficiency.
What do you mean week 4 bluish ting ?

rkymtnman said:

i still think you should try Lucas formula for a week and see what happens.
1:2 micro to bloom. 5mL /10mL should put you close to 1.2 EC. if not, 4/8.

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What do you mean if not 4/8 ?
The leaves are quite green so maybe less grow would work.

fartoblue said:

What do you mean if not 4/8 ?
The leaves are quite green so maybe less grow would work.

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5 mL micro and 10mL bloom per gallon should get you close to 1.2EC if not, try 4mL /8mL. if i remember correctly, 5/10 got me to 1.2 ish EC. i think 4/8 was around 0.9. but don't trust my memory!