What I have found is the plants are getting to much nitrogen in the soil mix... Therefore :- look at burning some green material( once it drys out with paper etc) or buy a bottle of POTASH, and mix into water, and give regular feeds of it. This counters the non- flowering stage, and kick starts ya fruiting cycle on your plants ! I had the same problems years ago, and a old bloke passed this trick onto me. I now use potash to self induce my passion fruit vines, with the best results ever seen and recorded for the fruiting vines around us here.... # my own dad swore by the use of potato e manure on his! but I never found it doing much for my plants! until meeting another old hand from the market days of yesteryear. Hope it helps ya..

- Derbyiter