I can see that some of the leaves are curled up with a fine webbing around them. If this is so this could be the beginnings of a spider mite infestation.

Thank you for your swift reply - diagnosis is spot on. :-)
Upon a closer inspection this morning I found the culprits, but discovered more: a snail on one of the top branches, a bright green caterpillar, and stripped bark. I will now be looking for some organic treatment.