Posted: 23/06/2015 at 11:38
Without a picture it is not easy to be accurate, but it actually sounds like Mildew. That is caused by dryness at the roots more than anything else. Try spraying with a 9 parts water to 1 part milk solution and giving the tree a really thorough soaking, despite the rain.
Definitely not Silver leaf which as you say does not affect Apple trees. Nor is it due to lack of pruning.
You could prune off the affected new growth if there is no fruit on them. Look up Summer Apple tree pruning on the Interweb thingy.