soft shells, grit .. DE and more. Questions from the backyard

I did a search but didn't find much for answers to my exact question. One of my Khakis is laying partially soft shells. I know oyster shell is the answer BUT

there is oyster shell in their feed (they are new ducks for me so two weeks on the new feed and she has just begun laying in the last four days.) I am feeding Scratch and Peck Layer formula and the other eggs are fine and there is a drake eating the same feed.

Should I add more oyster shell to their feed, add a free choice box of shell to their yard or just wait this out a bit. The other girls don't seem to need it and I'm worried the drake will get too much of it when he really doesn't need any.

I grew up on a farm and Mum just always put oyster shell in a box and let the chickens and ducks free feed but she was also only feeding chopped grain, while I am feeding something that already has oyster shell in the feed. I don't want to overload them if it isn't necessary.

One other concern I have ..

I put out a box of grit and they don't seem to be touching that. I'm not sure if I should add some to their feed for a little while. Their crops are HUGE! .. but to be fair they were neglected and thin when they arrived so I can't blame them for being little piggies around this yard full of slugs, worms, snails and good food in a bucket too.

They are foraging well and maybe don't need additional grit?? Again, I'm used to farm animals and we never fed grit because they had more than enough gravel around the farm to pick through but these ducks are in a back yard and it's mostly grass compared to the farm yard.

Edited to add: I am putting Diatomaceous Earth down in the bottom of their coop and I think they are eating that because they shuffle through the bedding and I hear their beaks tapping the floor. Should I give them some of that to eat too?

All advice appreciated.

 

Interesting .. I have 3 Khaki Campbell ducks and 1 drake that I got as adult ducks. I have been getting 1 egg a day since they first arrived. Then after about a week of settling in I started getting 2 eggs a day and then, once a week I get 3 eggs a day.

The soft egg is always on the day I get 3 eggs. At first I thought one of the ducks might be past her egg laying days but now I'm starting to wonder if perhaps the smallest duck is much younger than I estimated and maybe these are her first eggs.

As a kid on the farm the first eggs from the chickens were always perfect eggs, just tiny and sometimes missing a yolk but these duck eggs are full sized, soft as paper, the yolk has no proper sac and even the albumen seems as if it has nothing containing it. It's just all glooped together.

The last soft egg was mostly hard with a few soft spots but this second one is soft all over and broke almost as soon as I picked it up.