If you could tell us where you are, and also post a picture of the trees, it will help us to help you.
How big were the trees when you planted them? Are they growing in full sun? Near any other trees? If too near to big trees, the root systems of the bigger trees could be robbing the pears of nutrients and water.
Are they ornamental pear trees? Tons of white stinky flowers in the spring? Many blessings for a safe weekend!
