Citrus dropping fruit

turmeric

Morning everyone, is there a reason why my little lime bush/tree(?) would be dropping all of the developing fruits?  They get to about a centimetre long and then fall.  When I bought it last year it had about 10 fully developed fruits which I used.  This year it's put on about 6inches of growth and lots of lovely flowers but the little fruits just keep dropping off.  Any ideas?  Many thanks.