Unless it's the deciduous Daphne mezereum rubra, a great many evergreen and semi-evergreen varieties do tend to turn yellow, before dropping their leaves. As you point out there are plenty of buds which will, in time produce the new leaves. So I shouldn't worry. Having said, they can also do this if they become too wet when planted in containers.

Hi Huffmaling. My Daphne bohlua's leaves turn yellow before they drop off and it loses a lot of leaves every year after it as flowered. It is blooming now and I know it will drop leaves pretty soon.