Is my tree poorly?

Hi all, i'm new and this is my first post here. I have no idea about gardening but my 3 year old and I are learning!

Two weeks ago we planted a pear tree - we followed the instructions carefully and have watered it well during the recent hot spell. But it's looking a bit sad; the leaves have drooped a bit and I've noticed that some of them have black patches on. A couple of leaves have gone completely black. What did I do wrong?!? Does it have a disease or is this normal? Please advise........ Thanks! Teresa.

 

The black stuff on the leaves is probably a fungal infection called scab, very similar to Blackspot on roses. AND the cure is the same, add some systemic fungicide to your water. It is fairly normal for Pears to get it. Remove and fallen leaves and do not compost them.
As for the health of the tree, you seem to be doing everything correctly so, all you can do is wait and see what happens.