Yellow leaves on marijuana plant

A question from a fellow grower:

I have 2 plants growing in a plastic covered greenhouse in Portugal
(seed planted 1st March). They seem to be growing very well, but the
bottom few leaves have turned yellow, I thought this might be because I
had shaded part of the greenhouse with green shade and I read on your
site that this was not the thing to do, so I took it down. No difference
in the leaves though, I would be grateful for any input as to why this

Sometimes lower leaves just yellow and die off and it might not mean anything. The ones in your picture look like it might be like this and yes sometimes the lower leaves will do this if they don’t get enough light.

Something else to think about is it could be do to lack of nutrients, are you feeding them anything? The soil alone in a potted plant will almost never be enough for the entire grow. Also often discoloring can be from a pH related issue. What is the pH of the water you give it, the pH of the nutrient mix after it has been mixed with the water, and finally what is the pH in the soil?

Thanks for the reply, I’m afraid I don’t know any of the PH values(my first go at growing for many years) but I will test everything to see what they are. Yes I am feeding the plants, they look healthy otherwise I think.