Why is this Muscovy duckling so small?

[Quacking Pigeon]

My duckling never grew from day old size, the others were huge and this duckling was still as small as when it hatched.

 

[Kessel23]

I did not get his weight on hatch day but I think he grew, they are not that big on day 1 right?
btw, I am not sure how old these guys are but I think they hatched like a week or 2 into school so they would be around 3 or 4 weeks old.

 

[casportpony]

The small one, does it's belly look a little bloated?

 

[Kessel23]

it kinda does, it feels odd down there too.

 

[casportpony]

Day old Muscovies weigh 55 to 65 grams. Your small one is really small, but let me check my notes to see what the normal range is.

 

[casportpony]

it kinda does, it feels odd down there too.

What does it's poop look like?

 

[Kessel23]

I should have taken a picture, he pooped all over the scale. I do not know if that would have been helpful though because I think he forced them out to try and get away. He pooped 3 times when I was trying to weigh him. They were very dark green and a little watery, they smelled awful to. It was not the kind of green that birds poop when they are starving though. I caught a gosling when I was a little kid and he pooped all over me and it looked the same, dark green and awful smelling.

 

[Pyxis]

Alright I am back at home, I will go and catch them and weigh them now. I also need your opinion on the two normal ones, I wanted to know if they are hybrids or pure Muscovies. They look black and white to me which should not be possible because all of my breeding Muscovies are either chocolate or white. I do have the one pied drake but he has never bred with a duck so they can't be his kids, he is actually scared of the other ducks and rarely goes near them. I saw my Pekin drake mating with the Muscovy hens earlier in the year when they were laying their clutches so I wanted to know if you think the other ducklings could be hybrids. I will be back with pictures and weights in a little bit.

@Pyxis or someone else can correct me if I am wrong, but I think that white just cover up the base color. Go ahead and post pictures though.

One copy of white makes a pied muscovy. So for instance a solid chocolate female breeding with a white muscovy male that doesn't carry chocolate under the white could indeed yield black and white offspring.