Hello Beechnut52.
What an interesting coincidence....for the first time ever, my P. piresii just recently started producing buds as well. Somehow, the species must just know that it's time to start blooming. Just like you, the first bud was fully developed and poised to open, and then shriveled and fell off. Fortunately, the second bud fully developed. I was thrilled to watch the flower dramatically open this morning before I went to work. Absolutely spectacular. A HUGE, bold, striking, vibrant orange flower. I can't believe I haven't grown this one before. It will definitely have a prominent place in my garden this summer. The red flower buds are another cool feature of this Passiflora.
The only advice I can offer is to keep trying. I upped the watering on mine when I saw the buds, thinking that the extra growth would require more moisture. I also mist mine thoroughly a couple times a day. Make gentle changes until you find what works best. I'm sure you'll be posting flower pics soon!
Addressing your question on yellowing leaves is a real challenge, as they can result from myriad reasons. I grow about 35 species/hybrids of Passifloras (all indoors now, of course...last I checked it was 10F outside here). This time of year, with light levels so low, I welcome slowly yellowing leaves on my plants. The plants should be operating at a slow gear, "resting" if you will. I just make sure that they maintain at least a bit of new growth at all times - few Passifloras truly go dormant and lifeless. An important point - make sure your yellowing leaves aren't caused by spider mites. Some species/hybrids are very susceptible to them, others don't seem bothered by them at all. I personally have never seem them on my P. piresii, but that is just my experience.
Good luck with your new obsession!
Erick
