Thanks for writing in to us. Sorry to hear about your Witch Hazel.

This appears to be the symptoms of a relatively common fungal infection called Phyllosticta Leaf Blotch (in this case, specifically, Phyllosticta hamamelidis). The best approach is to remove the infected foliage (although tedious, this would best be done by clipping/plucking off symptomatic leaves individually since pruning back entire branches would remove too much growth) and discard those leaves, plus to discard any of the plant's fallen leaves that can be collected in autumn as well. This will reduce the amount of spores that overwinter near the plant to generate next year's infection. Spraying with a fungicide isn't recommended, not only because it can't cure an existing infection at this time of year, but also because this is a relatively minor disease from the perspective of long-term plant health and pesticide use risks harm to beneficial insects or other organisms.

More detailed information can be found here.

Let us know if you have further questions.

Lesley

DC Master Gardener