Duck laid soft shell egg and half sized harder egg within 10-15 mins

[Moments]

I have a close to 6 month old Welsh Harlequin who I noticed slowing down and breathing on the heavy side, laying down, tail down, wings down. She has laid and egg this morning so I was concerned she ate something she shouldn't have or a blockage. Within the hour just before 2pm she did a clear poop when standing and maybe 5-10 mins after that she laid a soft shell egg. Still breathing on the heavy side she stood next to the water bucket and shortly after laying the soft shell within mins another egg, which was harder, about half the size and not semetrical. She's still not moving much, she's usually very actively foraging, and is just standing with tail slightly down. Does it take a bit for their behavior to go back to normal after? When my runner had similar symptoms and laid a soft shell she was right as rain after. I've never had a duck lay one egg right after the other and she laid a hard shell first thing this morning. What could cause her to lay like this? She gets oyster shells available at all times

 

[Miss Lydia]

How long has she been laying? I've had a few females that didn't look good at all and they laid a soft shell and took a while to get up and go back with the flock. I think it is harder for them to lay a soft shell. Keep an eye on her since she laid another one soon after, hopefully just a fluke.

 

[Moments]

How long has she been laying? I've had a few females that didn't look good at all and they laid a soft shell and took a while to get up and go back with the flock. I think it is harder for them to lay a soft shell. Keep an eye on her since she laid another one soon after, hopefully just a fluke.

She's been laying for about a month. I've seen soft shelled eggs for awhile with new layers but never 3 eggs in a day. First one being hard and normal, with two soft shells literally one after another within minutes of each other later on in the afternoon. She wasn't pushing or panting, just breathing heavy and seeming lethargic. She's been fine ever since a bit after laying the third egg. Do you know what causes this to happen

 

[Miss Lydia]

I do not know for sure but here is some info that might help.
https://www.backyardchickens.com/articles/common-egg-quality-problems.65923/