I had success using a bio fungicide last year.
https://www.amazon.com/gp/product/B076HW6S9K
Though I also pruned a lot of leaves for airflow.
I’ve used this on other annuals and perennials on my garden with good success at preventing fungus. I’ve started using it this year on tomatoes, but it’s too early to say. I got it after reading up on it, and it sounds very promising. You do want to both spray leaves and soak the soil with it, but you only use like 1 tbsp per gallon of water. So it is pretty concentrated. It also needs to be used every couple weeks according to the package.
My Jade had the same exact weird shriveled leaves and black spots! What ended up working for me was this: Bonide Revitalize BioFungicide I sprayed her down thoroughly then poured the leftover solution into the soil as a soil drench. One application and not a single leaf has turned black since!!
It looks like fire blight, you need remove any infected branches. Dip your pruner in a 10% solution of bleach and water between cuts to prevent spreading it further. Then treat it with Agristrep. I would also recommend after that treating with a biological control. Agristrep: https://www.amazon.com/Fertilome-Fire-Blight-Spray-10363/dp/B005XOPBCU?th=1&psc=1 Bio control: https://www.amazon.com/Bonide-Revitalize-Fungicide-Concentrate-Ounce/dp/B076HW6S9K/ref=sr_1_11?keywords=biological+fungicide&qid=1686275990&sr=8-11
Bonide Revitalize BioFungicide I sprayed her down thoroughly then poured the leftover solution into the soil as a soil drench. One application was all it took!