Hmm
A tricky one. Firstly it is a Decaloba which means that it will not be trying to die back over winter like P. incarnata for example. I have not grown this particular Decaloba species, but the first thing I suggest for any rare plant is to take cuttings and share them about just in case. Also tip it out of the pot to check the roots-they should be nice and white-too many brown roots suggests that it is too wet-if in doubt keep it on the dry side. Its variations may be caused by roots rotting then it producing new ones. It may benefit from being repotted or given a high Potassium fertilizer. I use Rosefood or Ericaceous plant food. Tomato fertilizer will be ok too.

I also think that your winter routine with artificial light may be stressing the plant. Decaloba will do well over winter in a South facing window with natural light and most importantly water sparingly from below only and keep an oscillating fan on it. The fan helps keep the plant transpiring and is more important than anything else to help overwintering. When moved out leaves grown indoors are not suitable for outdoor use-so the plant usually disposes of them to grow fresh ones-very stressful. So move out into full shade to start with and later progress to full sun. Further if you put it out to early it can induce a type of dormancy.

It may also have predator problems-red spider mite are tricky to spot-check under the leaves with a magnifying glass.

Hope this is of help.
Myles

Here is a link that might be useful: Passiflora growing tips.

Myles,
Thank you for your input. I indeed agree that the winter light is a problem, this winter I will setup as you have suggested and see what happens. The roots look healthy and I tend to err on the side of under than over water, as for food I use miracle grow every other watering which nets to twice a month. I believe I will try a higher potassium formulation as you have suggested.