Trees Not Too Healthy?

Hi there,

Last summer I planted a number of mature pivet trees in my back garden exactly per instructions. To my eye they are looking increasingly unhealthy, and some are dropping a lot of leaves. Some of these leaves are torn, and blackened to some extent (see photos).

Any idea whether this is expected at this time of year?  Are the trees just dropping last year's leaves ready for new spring growth, or is there something bad occurring?

Many thanks.