Answer: Sunscald can turn the leaves yellow, as can a need for iron. Sometimes the oldest leaves yellow and fall, for no particular reason. So, if the leaves are crispy around the margins, it's sunscald. If the veins are green but the rest of the leaves are yellow, the plant needs iron. If the oldest leaves towards the center of the plant are turning yellow, it's normal aging. If the newest growth is yellowing, your plant needs to be fed. Overwatering can also cause the leaves to yellow. Hope this information helps you determine just what the problem might be. Best wishes with your yellow bells!
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