Leaves turning yellow

Overall your plant looks pretty healthy, you might have a slight nitrogen deficiency or your plat may be using up the nitrogen in the lower leaf, Because nitrogen is one of the most common nutrients that you’ll find in marijuana, it’s also common for it to be deficient in some way. Nitrogen plays an important role in many of the plant’s functions including the production of amino acids and the vitality of photosynthesis. Any deficiencies of nitrogen in the marijuana plant will manifest themselves first in the yellowing of the leaves. The leaves will start to curl in and die if the deficiency isn’t treated fast. The deficiency works its way up from the bottom leaves to the top leaves. Hope that helps and good luck to you