Different stages might be because all eggs arnt getting same amount of heat
Try placing all ur eggs in one place putting eggs in other places of incubator can affect it
And r ur eggs all at one hight?
Eggs that r higher experince more heat as hot air travels up
You can stop turning 3 days before lock down because I don't know in ducks but in chickens after day 14 they get in hatching position it's not needed to turn eggs