Help - No Eggs from Khaki Campbell

[DewittPondFarm]

Is it possible to have an infertile duck? I have three Khaki Campbells. One male and two females that are about one year old now. One of the females lays eggs daily without fail since coming of age last summer (even through the winter). The other gave a couple eggs last year at the end of the summer and never again. The male seems to pay no attention to her and only mates with the one. Could something be seriously wrong with the one who doesn't lay?