7litters is sure small for a rez, but that looks like a potassium deficiency. How often do you change your water?

once every two weeks, why?

mmm.. how could that happen if I'm using the nutrients in the recommended proportions? Should I increase the amount?

I've ran DWC. It would have to be a minimum of a 20 gallon (75L) resv. for me to try it again. F/D I do a total change @ 50% consumption

jj

I'd bet it's root rot. Let's seem them roots.

Also once you have added the amount of water you started with, you do a 90% change.

So once you add 7l of water and nutrients.. Change it.

I will say this, I think it will be impossible to grow with such a small water capacity. Once you hit late flower idk how you will keep it stable.

What is your EC, and temperature? Looks like your conductivity may be a little low, definitely loosing pressure, looks over watered but it being hydro and all makes that impossible lol those hooks and burnt tips also scream nitrogen toxicity

Hydrodev said:

Nutrients I'm using: sensiA&B 3.5ml first 2 weeks, 7ml third week and now 14 ml each week. In a water container of 7L. pH always around 6, temp ranges between 23 and 26.

Only values out of range:
- humidity around 30
- water temp high as 22/23 sometimes

I thought that maybe some more experienced grower can give me some advice here. What could be the cause of this?

Best

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I think ppm/EC is a much better way to ensure the nutes are at the right levels than only measuring the amount you add to mix. Most companies have a recommended grow chart for dosing too. I am a new DWC grower, on my first run, and it's finally doing great! I have each plant in a 5 gallon bucket.
When I started I was using a small AeroGarden type thing to learn from, it is trash, but was free to me. I learned that the smaller the reservoir you more you have to be on top of it. I went through root rot, defencies, excesses, all of it. My pH was a constant battle, I had to bring it down from above 7.0 multiple times a day. I had problems. I had been using tap water, and only measuring the amount of nutes, not PPM/ECing it.

1) I switched to a zero ppm water
2) got a ppm meter
3) sealed off any light going into the reservoir
4) Purchased Southern AG Garden Friendly Fungicide

and now that thing runs sooooooo smooth. So smooth for less than one gallon reservoir! The ph is stable!

Here is a picture of the last day before I transferred them to big 5 gallon DWC, had to wait on $$$ and Amazon for grow supplies.
I think a small reservoir is harder, yes, but not impossible. It's my first time, and if i can figure out how to maximize a small reservoir that people say is impossible, than I think you will be fine with your setup, once you get it dialed in.

As far as nutes, I only use General Hydroponics Nova line. Their Grow/Bloom are one stop formulas and they work miracles! During the transplanting I add a little fresh aloe solution to the reservoir for what I believe is beneficial. I have used it in the small reservoir during the root rot in addition to the AG fungicide, and those roots were super healthy in a week.