Yellow stains on my plant

Hello everyone, I'm from Italy so my English might not be good.

I'm growing an auto flowering plant in a space bucket (https://www.spacebuckets.com) with led lights and 3 pc fans.
I'm using cactus soil for my plant.

After germinating directly in the bucket my plant has grown fairly good, but I started noticing that the leafs had yellow stains.

Any suggestion for what it might be?

Update:
I bought a pH and humidity tester for the soil.
The pH is between 5 and 6, but the humidity of the soil is very high.
Maybe the problem is the humidity?
If yes how can I reduce it?

Yes, this could be humidity. but pH is not good. pH needs to be between 6 and 7.


to make pH better use Dolomite Lime. be careful you don't use too much! with care sprinkle it on top of your soil NO MORE than like sugar on a donut! then water in. wait half a day then test pH again.


the Magnesium in the Dolomite will help your plants. young plants like yours are often sensitive to Magnesium deficiency.


Ciao ...