Autopot, Jack's, Coco and a deficiency or two

This is a GDP in coco & perlite 60/40, using Jack’s 321 and is in a autopot springpot. Under a HLG 260 Rspec. Yesterday I noticed a few brown spots that I take to be a calcium issue. It has also exhibited what looked to me to be magnesium deficiency. To address the Mg deficiency I increased Epsom Salt by 10%. Sometimes in consecutive feeds and other times skipping one.
I have one other GDP that is starting to show Ca deficiency but to a lesser degree.
During a previous grow similar issues arose and I never really solved the issue. This time I am wanting to get in front of it and deal with it now rather than later. Untreated I know it will worsen.

It is tough to get decent overall plant photo because of the frame, but…

These leaves are one level below the tops

These are on the bottom or near the bottom. In some respects they also look hungry

I wanted to run this by you before I did something stupid. My first thought is to drain the reservoir and put a couple of gallons of 5.8 pH plain water (mix of tap & RO - 50ppm) back in the reservoir. Give it a day, empty and refill with Jack’s and MKP (just flipped and starting 2-2-2-1.2 MKP mix.

The last six feeds were:
date / pH / PPM i

3/2/2022 5.8 900
3/6/2022 5.8 890
3/8/2022 5.7 870
3/11/2022 5.7 850
3/13/2022 5.9 1110
3/17/2022 5.7 960

@Nicky @Pinboy @PharmerBob @The_Phantom_Reefer @emgoldslo @ash93



I wouldnt feed at 5.7 pH in coco. I stay between 5.8-6.0 could’ve been nute lock out because of the low pH. The plant overall looks good in my opinion. Its just a few leaves that look off.

Without the MKP, what are your measurements for jacks?
How far are your lights and what wattage?

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Possible to just turn the reservoir off for 24 hours. Fill pots with cal-mag dosed / ph’d water and then turn reservoir on another 24 hours later?

I have not started MPK yet so all of the reading are straight Jacks 321. I add FishSh!t too.
I start pH a little lower because it will drift up in the reservoir.

I did think of that too. Add directly to tray a couple of times.

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I know, but what are your jacks 321 measurements for each component?

You only provided us with the measurements including MKP. If you answer the rest of my questions I might be able to help you more.

Overall, I think you’ll be fine.

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Looks a bit like K deficiency too. Any very yellow leaves hiding in the brush?


Some misunderstanding. All of the readings from 3/2 to 3/17 is straight jacks before adding MPK. I have not started MPK yet.
Part A 3.6 g/gallon
Part B 2.4g/gallon
Epsom 1.2g/gallon


Hmm? Maybe I can’t tell the difference between Mg or K deficiency. However, I wonder if it some sort of pH issue cause lock out.
I drained the res and will put in 10L with CalMag and MKP pH to 6.0 ppm 490


They are very very similar in my experience.

Calcium tends to spread like a wild fire. Lots of yellow,orange, and brown dots spread over a bunch of leaves.
Phosphorus (not potassium, my bad…) is slower and more spread out. Calcium dots pop up everywhere, phosphorus a few leaves at a time, then it yellows out as well. Calcium tends to kinda burn up…


This is it. I had to increase Epsom to 1.4g per gallon and it fixed all my mag def issues. I had the same issue as yours.


I run the 321 with 1.4g/gallon on epsom all the time. I believe @Not2SureYet told me to increase it to that.


That is what I have been using. @emgoldslo I just got your seeds off today. Sorry. Has been a crazy 2 days. I will catch you in a few to give a tracking number :grin:


Thanks @Not2SureYet. They will be part of my next grow. My purple lemonade that I was going to send you a couple aren’t popping. I had 3 so far not germinate and hoping the last 2 take :frowning:


He advised me the same and thats how my problem was fixed. @Not2SureYet knows what he’s doing


@ash93 @emgoldslo @Not2SureYet Thanks I have done Epsom salt for the most part at 110%. So at 1.32 rather 1.2 grams. Not quite 1.4g



I just scrubbed my flower reservoir and actually did epsom at 1.6 because I saw a couple brown spots.

I never go under 1.4.


Have you checked the ph in the trays?


Add extra to your Res, add 0.2g per Gallon of magnesium.

Otherwise you could run water for 24hr and then run 0.2g per gallon.

Ph it to 5.8

Should get better.

If it still gets worse then add 0.2g of part A they may be a nutrient hungry strain.


I did not check trays. Good thought. I will next time I have an issue. Didn’t think of it this time. I did check the res. and it was 5.7. It did not have time to drift up because it was just filled the day before.
@ash93 I drained the reservoir and replaced with pH 6.0.

Going forward I will increase Epsom salt to 1.4g / gallon and up @Nicky Part A 10%