Hmm....
I've only got two grand dukes and two sambac.
But. In my experience.

They lost all leaves a soon as I planted them. They remained sticks for many months.
And then they burst into life, and everything is growing great since.

Mine like it dry. I water maybe twice a month. Too much water and the roots rotted.
I've never had any luck with that mix. Just doesn't jive with me.
My jasmine are all planted in straight composted horse manure.

I keep them in the upper threshold of gardenia light. So strong partial sun.

I fertilise twice a year with whatever's on hand.

And all in all I don't expect it to do anything till summer.
It hasn't grown a lick since August.

Hope that helps somewhat.

Hi Lynn!

So sorry to hear you're having troubles with your jasmines.
I can't give you advice for growing in your climate but I can give a couple of tips.
Can you grow them in filtered sun or an area with light shade?
Do you have a moisture meter so you can see when you need to water? You might be over watering or not watering enough. Sambac jasmines like a fast draining mix like the 5:1:1 (mine thrive in it). Maybe you're keeping the potting medium to wet or maybe you're not watering enough.
If you look at the 'Jasmine Sambac leaves turning yellow' thread you'll see lots of tips there.

Good luck!
-Robert