What damage is being done to your passion flower? Have you noticed any insects or insect eggs on your flower? I do know that slugs and snails can be a serious problem for the plant and these articles will give you ideas for getting rid of them:
Caterpillars, beetles and other foliage-chewing insects can also be suspect. Sap-sucking insects, such as spider mites and scale, like to occupy the stems. Remove caterpillars and beetles off by hand and spray smaller insects with insecticidal soap.
I really wanted to suggest it was the passion flower caterpillar (Gulf fritillary) but they usually make an appearance in the fall.
For more information on the care of passion flowers, please visit the following link: