If it were just the flowers falling off, I'd say it because they haven't been pollinated and were never going to make fruit anyway. We have had a very poor pollination rate on some of our apple trees this year, and it seems to have depended on when they were in bloom. I think it's almost sure to have been something to do with the very cold spring we've/you've been having. Our pear trees, however, which blossomed earlier, in a mild spell, have got loads of fruit developing.

In the 2nd picture, I can see, to the left, what looks like a tiny apple forming. If that's what it is, and there are more of them in other parts, then the blossom drop is quite normal - the flowers have either been pollinated and are now shrivelling and falling, or are unpollinated and shrivelling because their day is done.
If, though, any blossom remains on the tree in a shrivelled state without falling, that might indicate Blossom Wilt, which is a fungal problem and which needs dealing with. However, the presence of a baby apple most likely means blossom wilt isn't present.