The GARDENA gardening expert
Now this will be a little complicated, Mr. K., but at the end, there will be a picture – promised.
It is good that you mentioned the spots on the leaves because that allows me to help you! The overall picture that you describe indicates that your daughter's trees and the neighbour's trees are standing too dense or are poorly ventilated. This leads to higher humidity that cannot escape. This, on the hand, benefits a leaf fungus which causes the described shot hole disease or also leaf spot disease (compare pictures online).
You can combat a leaf spot disease with nature-friendly agents such as Neudo-Vital Fruit Spray (by Neudorff). To combat the shot hole disease in the home garden, there is no approved agent at this time.
The agent is not the deciding factor because both fungal diseases are the result of a fundamental problem. It is important to let in enough light in for the cherries and to have better ventilation for the surrounding plants for an improved garden situation. Because – and now I will get to the point – the bloom damage should stop if what I have read from your description is the cause of the problem. With moist, cool weather in the flowering season and your prevailing microclimate which could cause a fungus, encourages bacterial infection and in the end, reinforces the effects of late frost.
Furthermore, the infected, fallen leaves should be removed to reduce the spore strain.