Pandorea is a tender evergreen. So the first question would be has there been a temperature dip? Secondly, have you investigated the moisture in the soil using a tell or other tool to feel deep in the pot? Have you lifted it from the pot and inspected the roots? Plants can droop from both under and over watering. And lastly why is the foliage covered in pale speckles? Is it infested with spider mites or something?

@floraluk2 To me the soil feels somewhat moist, definitely not wet. It could be underwatering. I will give it a good soak and if there is a quick turnaround I know it is water.

The temperatures have been warm so far this Winter, down to nighttime temperatures around 8C / 45F and in the day much warmer.

I do not have an easy way to lift it out of the pot. Once I do that what should I look for?

Here is a close up photo of the leaves. What disease is this? How do I treat? The leaf discoloration might be just pollen falling off a nearby conifer tree.

The water drench test makes immediately clear the plant is starved for water. It comes right back. I guess what has happened is the fast-growing plant had its roots fill the container, and it just requires more water than was sufficient in Summer?

media is a water management system.. and when it fails.. this is the result ...

the peat is either worn out and not holding or retaining enough moisture between waterings...

or the plants roots have so filled the pot.. there isnt enough medium to hold the requisite moisture..

either way..YOU need to water.. and not rely on a lazy self watering system.. until you can properly repot the plant in a larger pot with fresh media...

this is not dependent on the plant in the pot.. its just basic pot culture ... never forget.. the most important thing in a pot. is the media.. not the plant..

ken

I can't make out what is on the leaves, even in the closer picture. You need to investigate for yourself using a magnifying glass if necessary. Also try washing the leaves off. Anyhow, it looks like a terrible infestation of some pest, perhaps spider mites, so the plant is in a bad way quite apart from the watering issues. https://extension.umd.edu/resource/spider-mites-trees-and-shrubs

Btw it's Bower Vine, not Bower's : Pandorea jasminoides

@floraluk2 The plant looks quite vibrant after receiving enough water. I have no idea whether the leaf discoloration is even an infection. It might just be pollen from a tree.

Well, you can see it in person and I can't, but it doesn't look like pollen to me. Can you wipe it off easily?

@floraluk2 After a recent rainstorm, the leaves were wiped clean, so I guess some kind of residue fell onto the plant.

What confused me here was how the water needs of this plant changed so rapidly, and how it seemed to exhibit a greater need for water in the middle of Winter, which is not what you would expect. I need to get this plant in the ground soon.