Viburnum plicatum 'Popcorn' Zone 6

6-7' wide and tall

Planted 2013

This year, the leaf buds emerged and the plant was covered in thousands of white blooms. As the blooms faded, the branch tip leaves grew to normal size but the leaves along the branch stayed about 1 inch big. Many of those small leaves are either wilting or dying. The tip leaves seem fine.

What may be causing this? Thanks.