Egg issues

[chipens]

Help
Having some issues with my eggs.
Eggs after a few days get a mottled look on the yolk and watery whites also the yolk is quite fragile. Shells are fine, some have extra calcium deposits.
They look great within the first day but if they sit a few days the yolks get like spots on them, and whites quite watery (I know they thin in older eggs but seems more watery than usual)
Also having a few fertility issues I'm thinking could be related.
I tried to get a photo

 

[nuthatched]

What is there diet?
https://www.backyardchickens.com/articles/common-egg-quality-problems.65923/

 

[chipens]

What is there diet?
https://www.backyardchickens.com/articles/common-egg-quality-problems.65923/

Layer pellets and a bit of kibbled maize mixed through. They're in different pens for breeding purposes and have access to oyster shell grit in a separate feeder. They haven't had any medication and always have water avaliable. They get the odd vege scraps from the garden and kitchen.
These are the pellets they make up the most of their diet. https://shop.stockfeed.co.nz/products/sharpes-hi-lay-pellets-25kg