Ever green Daphney.
My Daphney always has lots of flowers this year is no exception, but the leaves are falling off, and now the flowers are going a blackish colour.
Inspect the plant for pests. Neem Oil can be used to treat most pest issues.
Make sure the soil is well drained. Daphne hate to have soggy soil and can die of root rot very quickly.
If weather was very cold it can cause the roots to become susceptible to fungal root rot.
There are some 10 different viruses that can effect the Daphne plant. Use clean tools to prune any damaged plant material away.
If it is just a few branches, try applying a systemic fungicide.
If the entire plant is infected there is little that can be done.