A client of mine was disappointed that her witch hazel didn't bloom. Isn't that the whole point of having winter interest? So what happened?
We decided that a cold snap nipped those pretty little yellow blooms in the bud. Do I know for sure? No, of course not. But using the powers of deduction, we decided that the missing blooms were weather based. The shrub looks healthy, the new leaf buds look healthy. The interesting thing is that there were a few blooms that actually opened-perhaps before the cold snap froze the rest of them.
If you really want to prevent having your winter pretties made ugly, you can protect them by wrapping them with landscape fabric or plastic that has some air flow. But then you have to look at a plant wrapped in a sack all winter. Your choice!