Viburnum (rhyditophyllum) looking sick

Hi - I have a viburnum that I planted last spring - just over a year ago. It was about 2ft tall. It has put out new growth, but within a few weeks of new leaves appearing they go black at the tip, yellow and drop off. I have given it a feed with a general tree and shrub fertilizer but there has been no improvement. Has anyone an idea as to what could be affecting it. I have another viburnum - the same species that does not have this problem.

Thanks!