QI have a lovely Malus Profusion apple tree, bought for a Mother’s Day about 35 years ago. Every year at this time it sheds hundreds of inner leaves. The outside ones are fine. Some shed leaves have a purple velvety mark on them.
What’s wrong with it?
You may also have noticed some black scabs on the fruit.
As your tree is ornamental, and presumably you don’t intend to harvest and eat the fruit, you could try a fungicide – however it’s hard to spray an entire tree and it will provide limited control. Your best bet is to remove and destroy fallen infected leaves and fruit from the ground which will reduce the amount of fungal spores that overwinter.