viburnum rhyditophyllum

Hi - I planted a viburnum rhyditophyllum in March last year and soon after many of the leaves turned yellow and dropped off. I thought it would recover, but this year it seems worse. The leaves turn black at the tip and yellow up to where they meet the stem - then they drop. Even the new growth has this problem. I kept it watered and have given it a feed a few weeks ago but it still looks very sick. I have another of these the other side of my garden and it looks very healthy. Could anyone give me some idea of what is wrong. I have a light sandy soil into which I incorporated planting compost. It is in semi shade.

Thanks
Ann