There are lots of unhealthy looking ones round where I live and perhaps it might be connected with the soil as I believe they like an acid one? They seem to do OK when young but start to look poorly as they get older. It would be interesting to hear what the others think.

Is this Sorbus Cashmeriana? It definitely needs neutral to acidic soil and ours has a cool root run and is well watered naturally. Beyond that this has been an odd year for lots of tress and shrubs.

How long have you had the tree?