Q.Plum Tree Disease
My Victoria Plum tree leaves are turning red with black spots on them , curling up . Some of the plums are shrivelling up .

Certified GKH Gardening Expert
This looks like the disease Xylella Fastidiosa. This is caused, usually, by leafhopper insects.
There isn't really anything to treat the disease, but you can maintain the symptoms. This article will help:
https://www.gardeningknowhow.com/plant-problems/disease/xylella-fastidiosa-disease.htm
This article will help you to care for the tree:
https://www.gardeningknowhow.com/edible/fruits/plum/growing-plum-trees.htm