It's in some mix of cannabis soil I had, with 30% added compost.
A tomato plant got the same mix and is doing just fine, this cucumber guy seems to be unhappy.
I checked the pH (mixed soil with some water and used my pH / EC meter) and it was around 6, so I thought it should not be nute lockout, cucumbers are supposed to be between 6-6,5?
I have no clue but I would guess it's iron, guessing from images I've seen, but I'm surprised how it could be lacking iron if a tomato is doing fine in the same soil.
Also whatever it is, how should I fix it?
It’s definitely chlorotic, but there are a ton of potential reasons for that.
Can you give us a brain dump of watering habits, environmental conditions (temps/humidity/light), fertilizer use, plant age & provenience, specific contents of the soil/compost used, etc?
I water earliest when the top looks dry and with a finger I dig in and it is not still dark and wet there. For a pot like this and a small plant like this, it does not need water more often than twice a week, depending on temperature.
Temperature is what it is inside, it was around 25 °C this week, humidity always has been in the healthy range around 45-60 in the last weeks.
I potted it into like 70% of this mix https://www.amazon.de/gp/aw/d/B0CZ78WNG3?psc=1 that I had from last year in my basement and like 30% of this compost https://www.amazon.de/gp/aw/d/B07NWY7R87?psc=1
Oher plants including a young tomato grow just fine with it.
Since I thought somehow it must be missing something I also fertilized it a bit with some CalMag (die deficiency looked like Magnesium or Iron, but I don't have special iron fertilizer so I just thought adding some Mg will not hurt in case it is in fact Mg).
Was thinking about buying iron chelate or what it's called, iron supplement granules.
Unless someone has a better idea.
That’s very helpful, thanks! Unfortunately, this one is over my pay grade - nothing you’ve mentioned seems like an obvious culprit to me.
You can definitely try iron supplements, but given that your other plants in the same soil are doing okay, iron deficiency doesn’t seem to be a super-likely cause either. You might be better off starting fresh from seed, given that cucumbers take off rather fast. Sucks to lose a plant, but you’ve given it a strong setup here.
Okay thanks, at least good to know I'm not doing anything obviously wrong.