Help ducks sitting on nests for proper time then nothing hatches

[Jackrat]

I have four female call ducks who have all been sitting on nests for over a month now . They’ve had on average nine eggs each . Last year all of their ducklings hatched and were healthy , this year only three or four of their batches have hatched and even then a few of the day old ducklings have died . I have candled the unhatched eggs and there are ducklings ( dead inside ). Can anyone tell me why last year everything was ok and this year it’s been a disaster .

 

[Miss Lydia]

Age?
anything at all changed from last year to this one?
feed?
add or subtract of flock members?
any other changes?
Let's get some Call duck members here
@WVduckchick
@Overo Mare
@shawluvsbirds

 

[Jackrat]

They are two years old . Feed and situation the same except last year they laid eggs outside and this year they were in stables . Some of the males maybe siblings .
Feeding the ducklings small
Holders range chick crumb . Females sat on nests throughout incubation .

 

[SilverBirds]

Are these different hens from last year or the same ones? Are the males that bred them last year the same as this years? If the hens were bred with brothers/sons/dads, then the poor hatch and ducklings dying is probably a genetic issue.

 

[shawluvsbirds]

You know... I just don't know.
I seem to have a lot of them that make it all the way to the end and internally pip and never externally pip. Sometimes I wonder if it's the weather conditions