Yellow leaves aren’t always a reason to panic, and can be a normal part of a plant’s life cycle. Unless brand new leaves are turning yellow or all the leaves change color at once, it’s likely just your plant shedding old leaves.
Overwatering and root rot are the most likely cause of problems in Common Sunflower, since they are sensitive to wet soil. The leaves may also appear to be curling or drooping. Less often, yellow leaves are caused by underwatering, nutrient deficiencies, or pests.
Replace soggy soil with fresh, dry soil and download Greg to make sure your plant never gets overwatered again!