diseased star jasmine

I have an unhealthy star jasmine. It is about 12 - 15 years old, and for most of that time was thriving in an old wooden barrel. About 4 years ago we transplanted it into a custom built, sturdy large wooden box. It has never been the same since. The first signs of trouble were that a lot of its leaves started getting spots, turning red, then brown, then falling off. This year it has been infested with small white fuzzy looking pests on the underside of its leaves. (see photo) I thought they might be woolly aphids, or mealy bugs? I've also noticed a few scale insects on it. Any advice appreciated.

 

I guess it did not like something about the change. Did anything beside the repotting change or is the plant in the same place as before? I'm thinking about moisture from an overhang or something like that. My first concern would be the soil or pot itself. Does it drain well? Soggy roots might produce these types of problems.

 

I think that the box is more water tight than the old barrel and that may be the problem. The soil is no different and the plant is in the same place as before. Do you know what the white bugs might be? I was thinking that because the plant was weakened it has become susceptible to other disease or pests?

 

The white deposits on the backs of the leaves look like Cottony Camelia Scale (Pulvinaria floccifera), which I've experienced on hardy kiwi vines and Pieris japonica.

 

Thanks - that certainly looks like what's on it.