Large Belly, could it be ASCITE

[chickens really]

To me that looks like a yolk passed when the egg was laid also. It can happen...How long has she been laying?.Do you Provide Oyster shell separately?
When Hens mature they become bottom heavy. The prickly ness your feeling on her belly is new feather growth. Her vent looks sore. Do you have a Drake?

 

[casportpony]

Yes I will do that. This is the egg I found today. I can’t say it’s hers but it made me think of the ascites.
Would that cause her to be losing her feathers like that. I am new to ducks and this is my first major issue I’ve had. I’m not sure what ascites is and how it happens and should I worry about my other 3 babies? Now I’m freaking out.

That looks like yolk, possibly from a broken egg in the same nest.

 

[stuka123]

I do provide oyster shell
She's been laying for about 5-6
I have a drake and 2 other females

That looks like yolk, possibly from a broken egg in the same nest.

a

That looks like yolk, possibly from a broken egg in the same nest.

That’s what I thought at first but it was the only egg.

 

[casportpony]

It's possible she or another duck ate the other egg.

 

[chickens really]

I do provide oyster shell
She's been laying for about 5-6
I have a drake and 2 other females

a


That’s what I thought at first but it was the only egg.

Only egg in how long?...Possibly they need more time..better explanation in detail

 

[casportpony]

Here is a link for you to look at:
https://www.backyardchickens.com/threads/bloated-duck.1131827/

 

[stuka123]

I don't believe another duck ate the egg, I have never seen them even attempt to eat an egg if there was a broken one laying around. I have three laying ducks, they are all pretty consistent layers. I normally have 3 eggs a day but since the winter is here it's dropped back, normally 2 a day sometimes 3.
So I'm not 100% sure if she has laid or not. I will check the cameras tomorrow and maybe I can see who’s laying.

 

[chickens really]

Colour the vent inside with food colouring..Then you will know..One red, blue and green...

 

[Miss Lydia]

Just put the food coloring around the outside of the vent the egg will still have color on it.

 

[Mama Runner]

I would look at the overall body shape. What this person may be referring to just might be a deep keel or a "layer belly".
Also, pictures would help us see if the bird's eyes are clear and shiny, or if he looks dull and disinterested in life.