Hi there OHG, yeah you have a magnesium deficiency you can tell by how the yellowing is on the edges of the leafs like that and spreading between the veins. If it was the normal senescence process you would have it more evenly across the plant and the yellowing looks a bit different . You should try adding calmag if you're not too close to harvest because it will make a pretty huge difference in potency. Hope this helps ! 🚀