My passionfruit leaves are starting to have yellow streaks and some immature fruit is falling off.

Hi Nancy, have a look under the leaves of your plants and you may find an insect is chewing the leaves, which is taking all the chlorophyll out of the foliage. If you spot this, you need to treat your plant with an insect spray. If there is no sign of a bug you may have a soil problem, with it either being too wet or too dry. In either of these cases it causes the same symptoms. A side dressing now of Tui NovaTec Premium and an application of Tui Organic Seaweed Plant Tonic will give the plant a boost.