What is my Passionfruit telling me?

My passionfruit vine took off like greased lightening when I first planted it 14 months ago.  It has climbed about 60ft up a happy plant in one of the neighbours yard.  It has also wandered about 20ft in each direction along our own fence, and also over the arch, although that is not really its preffered route.  It definitely likes to climb up more than anything!
I estimate that we (and our neighbours who share the fences) must have had about 500 passionfruit off that vine so far, and it is not about to stop any time soon..  We wait until the fruit drops and then pick them up. Perfectly ripened, and they can stay in the refigerator for at least a couple of weeks until quite wrinkled, but are still very tasty.  I have frozen some pulp but cant imagine a time I will use it, as there is never a time I do not have fresh passionfruit.
The base of the vine has woody passionfruit virus, but it is still going strong, covering over the old dead wood with new branches.  What a tangle!  The roots grow deep into what was my neighbours chook pen, but they lost most of their chickens over the wet season, and just have one left.  Now they are using that area to build up a compost pile.  I noticed that suddenly all the new growth has yellowing leaves.

 It looks to me like a magnesium deficiency,and think I will give it a dose of epson salts tea - something that I think is lacking in the local soil, as everything perks up after epson salts.  Does anyone have any other ideas of what could be causing this? 

Dont you find it awesome that nutrients travel all the way from the roots to the very tips of these plants to provide its nourishment?  Most of the time too they do it without any help from us, but this time I think my plant is calling out to me for some help.