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?
Okay, i need to know as well. Mine look the same. It has a cucumber baby on it, but otherwise it’s all yellow and dry:(
I water it every day making sure it never dries out
Well for one you probably shouldn't be watering it every day. If you keep the roots constantly wet, they'll rot and the plant will die.
Hm. From what i heard cucumbers need a lot of water. Was that wrong?
Sweeping generalization: they need lots of water, but they also need to be planted in a space that gives them a sufficient root base such that they can go a few days without drying out.
Yes/no, depends on if you water log them or not. You can also add some hydrogen peroxide to oxygenate the soil for around 24 hours in pots.