Duck egg problems

[fieldarcher]

I have two scary cat Runners about 1 year old I think only one is laying as we get a blue egg but when they both lay there is a white and a blue egg.
We also have 2 Cambellsl on POL,
Question is . We have started to get black bits in the yolks first it was the odd one from the Runner now my wife had one in a Cambell egg, thay are about 1/4" big,
I feed them with layers pellets with some crushed poultry grit and what ever they find in the garden.
Any ideas what the black bits are?

 

[Miss Lydia]

I have two scary cat Runners about 1 year old I think only one is laying as we get a blue egg but when they both lay there is a white and a blue egg.
We also have 2 Cambellsl on POL,
Question is . We have started to get black bits in the yolks first it was the odd one from the Runner now my wife had one in a Cambell egg, thay are about 1/4" big,
I feed them with layers pellets with some crushed poultry grit and what ever they find in the garden.
Any ideas what the black bits are?

@fieldarcher Welcome to BYC!

Here is a link to a thread about eggs and what we may find
https://www.backyardchickens.com/a/common-egg-quality-problems