I have nothing to back this up.. But the Passi's I have that have that duck foot shape leaf don't seem to like the heat and humidity here.. When they start pouting I bring them in the A.C. and they seem to perk up and do well.
Chena

That could very well be the problem Chena. It does happen around the same time every year and it's been close to 100 degrees with oppressive humidity for the past few weeks. I'll take a couple in the house and see what happens. I have some others with bat wing foliage but they don't yellow like the citrina does. I do keep this one fairly shaded. It was one one of my first passies and it took me a couple seasons of baking the poor plant in full sun before I realized that it needed shade. This plant(s) has bounced back from near death more times then I can count.
Karyn

I had my citrina in a window at home where it got 6-8 hours of sun a day, and after a while it started doing the same thing--leaf yellow, then curl, then brown and drop. Growth stunted. So I took it to my office at work, where there are no windows and florescent lighting. It's growing like crazy right now. Go figure! I'm just wondering if I've found the perfect growth habitat for a p. gritensis! ;-)

Come to think of it that particular passie does so well over the winter under the HID lights. I haven't brought them in yet but will. I just hate having plants inside. lol
Karyn

The leaf shape on those are very similar to my sunburst. I have noticed that sunburst does not like extreme heat. The heat here flat out killed one of them. All the leaves yellowed dropped and then the roots died. Luckily I have a few of them and some cuttings. Another has dropped its leaves as well. The small one is inside and doing great. I will have to move the larger one inside too. We'll see if it does better.
The Pink Festival passie doesn't seem to like this extreme heat either, though it has completely different leaves.
~Lenette

Pink Festival is a gritensis clone, and from everything I've heard, gritensis hates direct sunlight. You might try moving it to where it only gets morning sun and see if that makes a difference.

My Sunburst is in pretty much full sun and seems to be happy. I keep my sanguinolenta shaded but I'm still waiting for blooms on that one. I wonder if I have it too shaded? I'm just afraid if I start moving it into the sun it will fry. I did bring two of my citrinas inside and have them under a couple skylights. In a way I hope they don't do well because if they do I'll have to keep them inside as houseplants :( I'm strange. I love plants but really dislike having them in my house. I have a couple minimal care plants inside, a ZZ, philodendron and some African violets that have flourished for at least 10 years despite having never been fed or transplanted and they only get water when the leaves are completely limp.
Karyn

Have you tried giving them some epsom salts mixed in with water?

I give almost all my plants epsom salts once a month. It doesn't seem to have any effect on this particular passie. I think it probably does have to do with the high temps and equally high humidity. I guess I'll find out soon enough now that they have invaded the interior of my home. lol
Karyn