May Lotito wrote:Hi Gillian, welcome to the forum!
Is your citrus recently having a flush of new growth? If it's lacking certain nutrient the tree will move them from the older leaves to the new ones. Do you observe anything wrong with the new growth? I seem to see crinkled leaves. Top dress with organic fertilizer such as worm casting or compost will help. Or you may remove the root ball from the pot to see if it needs potting up.