There are several reasons why an apple tree does not produce a full bloom:
It is possible that the tree is too young and is just beginning to become reproductive, that is produce flowers. If this is the case, flowering should increase next year.
A young tree may be overly vigorous, spending its energy producing wood and leaves and not flowers. Over fertilization is a possible cause.
Flower buds are formed 10 or 11 months prior to bloom, that is …