Different Passiflora can have quite different soil needs from very alkaline to quite acidic. Ericaceous soils can be too acidic for some Passiflora and if too wet the roots will rot and the plant will die.
See link for more info and soil recipes.

Here is a link that might be useful: Passiflora soil

You learn something new every day... All mine are planted in the same stuff- El Cheapo "dirt".

Maybe someday I'll do some clone experiments- Same everything xcept potting soil- Is there a difference between 'cheapo' and 'spendy'? We'll see.