I too have planted apple trees this year and they have lost fruit which I believe is quite usual in their first year. They are using all their energy in their branches and trunk when they are young - combined with the lack of water at the moment.

This is known as June drop - the tree thins out its fruit itself by dropping some immature ones, leaving behind ones that will swell and become mature apples. Just keep the tree watered if you're in drought though, erratic or insufficient water supply can cause more to fall.

Also, a young tree may decide to drop most or all of its fruit the first year, may not bloom at all the second and third. It needs some time to get established enough to produce--smarter than people, sometimes!