Two years ago I planted a black passionfruit in a large pot in my conservatory. I regularly water it and feed and it grows vigorously. The major problem I am having is, it appears to get very tiny flowers only then to die before even developing. What do you think is happening?
Your problem could be caused by insufficient pollination. Although the black passionfruit is a hermaphrodite (has perfect/complete flowers) it needs insects for pollination. Often indoor plants need to be hand pollinated. Try using a soft paintbrush and gently brush the small flowers just when they open. If unpollinated, flowers often drop their petals and no fruit develops.
The problem might also be the fertilizer you are using, fertilizers high in Nitrogen promote vegetative growth, but can also inhibit flowering and fruit production, Just a thought.