Answer: The symptoms you describe sound more like a critter feeding than a disease problem. Holes in leaves, even with browning edges, are generally caused by caterpillars or beetles. A healthy plant tries to seal off the injury when tissue is damaged, so it's normal for the edges of the holes to turn brown. Since you haven't discovered the culprit, and it may be long-gone before damage is even noticed, I'd take a wait and see attitude. The leaves of the hydrangea will fall off soon, and you can prune the viburnum if the damage to the leaves is extensive.
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