Hi Jazzy have a look to see if any creature is in the curled up leaves. Is it watered and been fed recently. If you give a good broad based feed you might take care of any elemental shortages....potassium...magnesium....etc. A photo would be very handy. If there is an infestation, maybe soapy water might help as a first line of attack.

sounds like blackfly this happened with one of my trees .
I bought an organic spray to get rid of it.
You can actually buy an organic fruit spray for fruit bearing shrubs and trees from your local garden centre to get rid of bugs etc