Apple Trees failing to fruit

I purchased 3 new apple trees, one Bramley and 2 Cox 2 years ago and last year.

Last year they all fruited well, in fact I had to tie up the branches to a stake as fruit was on ground. I pruned the trees in the winter, about a third off the branches.

This year they blossomed but have not fruited and some of trees have a few shriveled leaves with what I think are aphids on back of leaf.

In general they still look healthy trees with plenty of growth this year but hardly any fruit at all.

Any advice would be much appreciated