Need Help with Nute Deficiency - RO Water

[Delps8]

Environment Info
Strain - AK-48
Number of Plants? 2
Growth Stage? Flower - week 1

How Long? 4 sets of nodes on 7/20/17 = 45 days
Indoor or Outdoor? Indoor
Grow Type - Hydro

Reservoir Size - 35 gals capacity, 28 gals to refill to 1/2" below net pot
Reservoir Temperature - 68 ±0 (Active Aqua chiller)
Medium - Started in rockwool

Hydro Setup - RDWC
Size (Wattage) of Light? How Many? 1 "600" watt LED, mfg says it draws 320 watts but KillaWatt reports 400.
Is it Air Cooled? Yes, cooled by internal fans.

Temperature of Room/Cabinet? Running a portable AC for the last week. Temp range has been 74 - 79.
RH - Average high about 72%, average low about 68%
PH - 5.8, has varied from 5.3 to 6.1

Pests - None known
Type and Strength of Fertilizers used? Fox Farm hydro nutes at about 50% recommended strength. Using the 420magazine.com "Wonder Chart" for analysis.
Size or Square Footage of Room? 2' x 4' x 8'

Using an EC + temp + pH monitor and really like it. Active Aqua water chiller is excellent for my needs. The RO unit feeds a 55 gallon cistern in the garage. The cistern temp is about 80 (August in Southern California) and the chiller brings the res down to 68 in < 6 hours.

Hydro unit has "top feed" which I shut off after the plants developed a good root system.


Problem Statement
Grow is in week 3 of flower.

My plants have had what looks like a cal mag deficiency for a couple of weeks. Strange thing about this two plant grow - "Norah" is 51" tall, "Nancy" is only 33". Norah has shown some signs of this issue over the past few weeks but none now. She is growing incredibly quickly and the only issue I see is some nute burn. I've pumped out some of the res to drop the PPM from 620 to 570 to try to resolve that.

Nancy is a different story. Compared to Norah, her growth is "stunted" and, she hasn't grown much during the stretch of the first few weeks of flower. Her leaves, per the pix, are impacted by what my newbie brain sees as a cal mag deficiency.

When I flipped to lower, I dicked up and used the wrong EC==>PPM conversion factor so I was using a nute level 40% above what I thought it was. Fixed that about a week ago. I've also had problems with pH dropping. For example, 5.9 to 5.3 (once) which tech support at Fox Farms and Botanicare indicated was nothing to be alarmed about.

For the past few days, the numbers indicate that the res has been dialed in. The plants have been taking on water, and PPM and pH have been steady at 600 and 5.9, respectively. I realize that 5.8 is optimal but I haven't wanted to change anything since the numbers are so consistent.

Since I'm seeing a little nute burn in Norah, I just pumped out out 6 gallons and replaced with RO water. The res at a 0.8 EC/570 PPM and pH is 5.8.

My concern is Nancy. Per the pix, it looks like something that CalMag could resolve but I'd appreciate feedback from "those who have gone before me". IIRC, a symptom of magnesium deficit is that the vein in the leaf gets lighter - I'm seeing a bit of that. The biggest symptom is that the leaves have light to medium brown spots and they appear on existing leaves but not on new growth. Per the advice of Fox Farms tech support, I've cut off leave that were heavily damaged by nute burn but I'm not keen on lopping off these leaves - the damage is on a limited surface area and my hunch is that maybe 25% of the large fan leaves have some level of damage.

I appreciate feedback on what steps to take to resolve the issue that Nancy is facing. Thanks much.

 

[AnimaSola]

I feed mine calmag and veg nutes for the first few weeks of flower until the stretch is over, looks like maybe Ca, hard to tell without a full plant pic.

 

[Delps8]

Luweedgi:

Uploaded a hastily shot pix - thumbnail below.

That's all there is to Nancy's canopy. There are no signs of nute_ burn (no tips are discolored) - just these damned spots! (Cue the voice of Lady Macbeth...)

My light can't go any higher and Norah is growing so tall that I had to supercrop her over to the right...over to Nancy's side of the tent. As a result, there's not much room left for Nancy.

I appreciate your feedback, amigo.

 

[AnimaSola]

Looks like Ca, P and maybe S deficiencies. Over/under watering, nute lockout, or root problems can show up as multiple deficiencies on the leaves. Garden gypsum will add Ca and a little S without affecting pH. If it has purple petioles you could probably up your flower nutes a few ml/gal.

 

[Scientific]

Really nice, thorough write-up!

I gave my hydro grow 50% GH nutes and had similar symptoms to yours when I cut back the GH CALiMAGic Ca/Mg supplement from 2.5 ml/gallon to 1.25. The water here is almost mineral free, so essentially RO. I have recently seen another grower here with the same problem when giving Advanced Nutrients nutes with RO but no Ca/Mg supplementation.

I e-mailed support at Advanced Nutrients once asking them why they listed their Ca/Mg supplement for use only with products other than their advanced products and they told me that you should never need Ca/Mg when using their nutes, even with RO. But it looked clear to me that in at least one case, someone using their stuff with RO got a Ca/Mg deficit by not supplementing.

Anyway, my guess would be that a Ca/Mg supplement would help here.

Good luck.

 

[Delps8]

Really nice, thorough write-up!

Scientific:

Thanks for the compliment about the write up. History major + >25 years writing software. Well, that's my excuse anyway!

I gave my hydro grow 50% GH nutes and had similar symptoms to yours when I cut back the GH CALiMAGic Ca/Mg supplement from 2.5 ml/gallon to 1.25. The water here is almost mineral free, so essentially RO. I have recently seen another grower here with the same problem when giving Advanced Nutrients nutes with RO but no Ca/Mg supplementation.

I e-mailed support at Advanced Nutrients once asking them why they listed their Ca/Mg supplement for use only with products other than their advanced products and they told me that you should never need Ca/Mg when using their nutes, even with RO. But it looked clear to me that in at least one case, someone using their stuff with RO got a Ca/Mg deficit by not supplementing.

Anyway, my guess would be that a Ca/Mg supplement would help here.

Good luck.

Interesting that you've had the same experience. Also, I just got the same info from tech support at Fox Farms.

I've been in touch with them on the nute burn issue so I called back this AM. Turns out that I bought the wrong version of Grow Big. I've got the soil version but should have the hydro version. That'll be here this evening so I'll be doing a res change yet again.

Jared, tech support at FF, said that since I'm using GB for soil, I'm missing a couple of trace elements that CalMag wouldn't make up for. I'm hoping that all will be better once I get the res swapped. It's not only the nute deficiency but the fact that my pH is plummeting - 5.9 at 1930 yesterday (lights out 2000 to 0800) which was down to 5.0 at 0900 today.

I'm hoping to resolve both issues with the right version of GB and a res change.

 

[Delps8]

Looks like Ca, P and maybe S deficiencies. Over/under watering, nute lockout, or root problems can show up as multiple deficiencies on the leaves. Garden gypsum will add Ca and a little S without affecting pH. If it has purple petioles you could probably up your flower nutes a few ml/gal.

Luweedgi:

Yup, you were right – it's more than just CalMag. New grower steps on his...thumb. I was using Grow Big for soil instead of the hydro version.

Fox Farm tech support listed off a handful of trace nutrients that's not in the soil version so those aren't being provided for my grow. I'll have a quart of Grow Big here tonight so I'll do yet another res change but I'm hoping this will clear the nute deficiency as well as resolving the plunging pH problem.

Thank you for the info, once again.

Just found the "thank" and "like" - good on ya!

 

[Scientific]

Jared, tech support at FF, said that since I'm using GB for soil, I'm missing a couple of trace elements that CalMag wouldn't make up for.

Hmmm... they're called trace elements for a reason. I suspect that with good soil and commercial fertilizer preps, actual trace element shortages are rare... Just my .02.

 

[Delps8]

Hmmm... they're called trace elements for a reason. I suspect that with good soil and commercial fertilizer preps, actual trace element shortages are rare... Just my .02.

Agreed. There's not much to them but, seeing that there were zero of those being provided, I can understand their belief that this is the fix.

To add to the confusion, one plant is doing fine (it's doubled in size so far) vs the other which is much smaller and is having problems. FF TS suggested that perhaps the root system is has been damaged or compromised. That, too, is plausible. Norah took off when I switched to flower. Nancy's barely grown since veg - she's developing flowers but nothing like Norah. Think of the movie Twins (Schwarzenegger vs de Vito).

 

[Scientific]

seeing that there were zero of those being provided, I can understand their belief that this is the fix.

If you are feeding the recommended trio of FF hydro nutes, all of the trace elements (now often called "micronutrients") will be in there. (Grow Big and Tiger Bloom say "Contains Trace Minerals" right at the top of the bottles.)

 

[Delps8]

If you are feeding the recommended trio of FF hydro nutes, all of the trace elements (now often called "micronutrients") will be in there. (Grow Big and Tiger Bloom say "Contains Trace Minerals" right at the top of the bottles.)

Agree completely.

The issue, according to FF TS, is that I'm using the soil version of Grow Big instead of the hydro version. I hope the hydro version gets here 7 PM or so because I'm doing lights out at 8 PM.

Oh, "micronutrients" vs "trace elements" - thanks for pointing that out. I'm thinking "trace elements" from human nutrition.

 

[Scientific]

Oh, "micronutrients" vs "trace elements" - thanks for pointing that out. I'm thinking "trace elements" from human nutrition.

"Trace elements" gets used all the time in biology, in my experience, regardless of which kingdom. I was just commenting on usage in the cannabis community, where "micro nutrients" seems to be favored.

 

[Delps8]

"Trace elements" gets used all the time in biology, in my experience, regardless of which kingdom. I was just commenting on usage in the cannabis community, where "micro nutrients" seems to be favored.

Understood. Every specialty, by definition, has its lexicon.

Hey, the new version of Grow Big came in and I got the nutes mixed and the res changed, and everything buttoned up by 8:30.

I'll go lights on at 9 AM and we'll see what happens.