Soft shelled eggs for a month??

[Shayrae4]

I have 3 female ducks (2 Pekin, 1 blue Swedish). They are almost 7 months old and have been laying eggs for a month now. One of them has pretty consistently been laying soft shelled eggs every day. The other is mostly hard with the occasional soft shell, and the third lays normal hard shelled eggs every day.
They eat dumor all flock 17% and have a small bowl of oyster shells out. Both are free choice. They don’t seem to touch the oyster shells unless I sprinkle it on top of their food (which I have only been doing every couple days). Anyone know why it’s soft? I know soft shelled eggs are common in young layers, but I’m curious how long I should give her body to work it out itself?

We also live in central California where it’s been really hot (like 100 or over every day). Maybe this is why? They free range in my small suburban back yard 24/7, so they have more than enough room.

 

[Isaac 0]

As you mentioned, it is not totally uncommon to have a member within the flock, especially at this age, with egg abnormalities.
The reasons for this issue will vary by case; some birds may simply not be getting enough calcium in their diet, or are still familiarizing themselves with the egg-laying process. Heat, stress, genetics among other factors can contribute to this, but it is not something easily diagnosed.
In many cases, the soft shells can be corrected by administering the bird a calcium supplment.
Several, such as calcium citrate, or calcium gluconate can be used on ducks. If have inquires regarding the dose, please post back with the calcium type, and milligram content.
https://www.tractorsupply.com/tsc/product/durvet-calcium-gluconate-500-ml

 

[Jlw0903]

I JUST posted about the same problem. People were giving me a lot of different advice.
https://www.backyardchickens.com/threads/you-can-lead-a-duck-to-oyster-shells.1483126/#post-24719993