Brown marks on the unopened flowers are a sign of botrytis rot, a fungal disease. Botrytis can be treated by spraying the buds with fungicide before and after they have opened.
Die-back of the leaves from the tip to the base can be caused by a fungus known as Macrophoma agapanthii. This fungus can be treated by spraying the entire plant with fungicide.
Snails love to shelter in the leaves of agapanthus plants. Fortunately, they don’t cause much damage to the plants and are best dealt with by picking them off by hand when you spot them.
Yellow leaf tips indicate overwatering or waterlogged soil. You can rectify this by adding extra organic matter, like compost or bark chips, to the soil.
