Different shades of green indicate something?

Thanks for the replies, guys. It sure does look like it. I have cal-mag added to my soil at 1kg/m3, magnesium 154mg/l. That should give me a moderate Mg level, from what I gather. But Cannabis seems to be a heavy Mg feeder, so maybe just needs more. I guess it could also be due to a problem accessing the Mg in the soil. humidity is stable around 50RH and temps never go under 18c. PH might be too low? My soil is supposed to be at 5.5-6.5, growing organic so figured it should stabilize itself. Thinking of giving some foliar spray with epsom salt. What do you think?

This is a magnesium deficiency in its beginning stages. the light green or yellow coloring will begin to show on the veins and edges of the lower & older leaves – this is one of the classic signs of magnesium deficiency. You may also see red stems. Magnesium is a mobile nutrient, which means that the plant can move it from old leaves to new leaves. If you don’t react to it promptly, a magnesium deficiency can spiral out of control and cause your plant to lose a lot of lower leaves quickly. The plant will pull magnesium out of older leaves and bring them to the newer leaves. That’s why a magnesium deficiency usually appears towards the bottom of the plant and on older, less important leaves.

Hey there , that looks like magnesium deficiency based on the yellowing between the veins starting at the base of the leaf affecting the new growth first. It’s probably just adjusting like you said , but you can add cal mag or even make a spray. The problem should stop spreading once you feed calmag and the plant should fully recover quite quickly. Hope this helps !