Evergreen spindle leaf drop?

I have a number of euonymus fortunei(variegated evergreen spindle) shrubs in my garden that I got as very small plants a couple of years back and they have been gradually getting bigger and I hope in time they will help brighten up my garden in the winter months when a lot of other plants will not have much colour. There are three of these in a row out of five that I have alternating with some rhododendron that recently have dropped most of their leaves. I show the issue in this short video clip. I think since they have held onto one or two leaves that they are not dead and am hoping they recover. They are in a fairly exposed position with the mature hedge next to them being fairly bare at the lower parts and being deciduous does not provide much protection from the strong winds I get here being close to the top of a hill.

It is the ones higher up that I have seen loosing their leaves so I am guessing it was caused by the recent cold weather and maybe some cold north westerly or north easterly wind gave them a bit of a shock when they thought spring was on its way. Just wondering if anyone knows if there could be another explanation? I can't see any sign of scale insect or a specific disease other than some of the shoot tips are after dying back as well but this has also happened on some of the plants that have held their leaves. Any suggestions appreciated. Some of the spindle I planted in more sheltered places are growing with no problem.
All the best.

 

I consider Euonymus fortunei semi-evergreen, so I reckon they will be fine. If you gently scratch away a little of the bark, close-ish to the tips, then if it is green underneath it will be fine.

Even so, I'd expect them to be bigger by now ... perhaps you need to talk to them more? I tend to say "Do you want to go on the compost heap, or what?"