I was at Ong's Nursery this weekend buying some plants, and got to talking with him since he was present (a rarity). He recommends applying a water-soluble 10-52-10 fertilizer twice a month to aid and extend flowering/fruiting. He said normally for example Wax Jambu just produces one crop in July but with the fertilizer it continues flowering/fruiting until November, producing up to 5 crops total.
But everything else I've read about high-phosphate fertilizers is extremely negative. Even water-soluble fertilizers in general seem to have a fair amount of bad things written about them. Of course Ong specializes in tropical fruits from southeast asia so maybe those have a higher need for high-phosphate fertilizer than other plants? Does anyone have personal experience with high-phosphorous fertilizer?
I'd love to extend the fruiting period but probably not if it significantly compromises vegetative growth.