Are you in the USA? Her diet is off she should be eating a good diet formulated for ducks or waterfowl first off if you can’t get that then it’s chicken feed either layer or an all flock with oyster shell on the side. Corn is not a good wholesome diet . I agree with @DuneDucks sure sounds like a laying issue. Calcium Gluconate is the go to for that 1 ml over a small amount of treat something she loves and will gobble right down.