HELP! D39. My 5th growth in row is failing. (1st with autopots) Yellowing TOP leaves. PH, zinc,iron, something else?

[Mañ'O'Green]

@BipolarBear91 Welcome to AFN.

Too much calcium! Your tap water is ~50 PPM Calcium and you are adding another 150 PPM on top of what is in the Canna Coco so probably ~275 PPM+ I like to run ~150PPM Ca

The numbers in the brackets is the max recommended.

This is causing a Mg lock-out.

 

[MoparMad]

I just read through quick. I am not the best leaf reader. But can say when I have seen that from the leaves. it has always been a mag issue. Also. If you are running a 80/20 mix of your water. Your water should be around 240ppm Not 50 or 60. I have been running autopots for years my self. I either use Jacks or GH nutes. Gh is mostly for top feeding any more. I also use Vermeculite instead of the perlite. Personal choice there. I re use my coco. And the roots stick to the perlite.
So you flush you coco good before the first use. if not. I would recommend it. When I first start out top feeding. I go extra heavy on the epsom or cal mag. Depending on the nutes using. Coco will steal some of the mag from your coco. So I always start heavy on that. And then back off a little as the grow goes on. Another option would be to pre charge the coco before you use it. Just a thought. Till you have things worked out. You can always use a 3 gallon pot in the autopots. I pretty much use 3s for all my plants unless top feeding. I am like @Del boy If I use the GH nutes. My may ppms are normally 650 or less. Basically 1/2 strength. My autos really slow down when getting fed to high with the GH.
This is just my O2. If you are going to flush. Use 5 ml per gallon of cal mag with each gallon of water. Don't worry about the ppms. Also. If your starting ppms of your water are as I think. That can be an issue too. My tap water here is 535ppm. I have hard water nutes. But find it is easier to just run straight Ro.
I will tag a long if you don't mind to see how things progress here.

 

[Olderfart]

Honestly, I think my lack of experience in growing and respect for authority did it.

Several people on autopot reddit use 100% coco, due to better wicking potential. However, it has been pointed to me, that that is scientifically unsound and coco only may not have better wicking potential than coco/perlite.

Oh, I think you mean soil vs coco.
I am doing both - kind of.
1 autopot and 1 5 gallons biobizz light mix organic grow.

Iwant to complte at last one "organic" grow before I go only autopots. Principle

For what it is worth, I have run autopots several times, both coco/perlite and soil. I have never been able to get through a grow without at least minor issue of nute buildup in the coco, and consequent lockouts of particular nutrients in at least a few plants. Also, I have never managed to have plants put up with more than about 1000EC, or (likely) 500ppm on your scale. As others suggest, I would flush. And I would do it with 500ppm nutes and no calmag. I doubt that there is anything wrong with your nutes, I think you are dealing with lockout, likely due to a combination of excess Ca as mentioned by @Mañ'O'Green, likely exacerbated by nute buildup due to the subirrigation design.

Take this as only my two cents, others here have done better with autopots than I have, and some make higher EC's work better than they have for me. I don't use autopots any more for salt nutes and cannabis, I have gone to automated top watering designed after Cocoforcannabis.com's suggestions. If you have not studied that website, and you want to continue with coco, you should review the entire site a couple times. It is the best information out there on the topic, but keep in mind that they are talking about top watering, the EC/PPM's that they recommend will have to be lower for subirrigation like autopots. I found ~900EC about right, which is more or less consistent with their suggestion of 1000EC once plants are well underway.

Good luck with it, and please report back on what you decide to do, and how it works out.