I have a problem...fertilized eggs?

[NHimport]

I go out to gather my duck eggs every morning. They're usually done by 8am. I have 5 Campbells laying right now, and had been getting anywhere from 2 or 3 to 5 eggs a day. Usually only 2 or 3 though. Well today when I went out there were 3 eggs in the hay, but as I picked them up, there were more underneath them. And more underneath THEM. I collected 13 eggs all total this morning! The problem is, I don't know how long they've been there! Each layer of eggs was covered with a lot of hay, that's why I didn't see them. I know how to candle eggs, but I don't know what to look for. I researched online what developing embryos look like, but when I look "in" my eggs, all I see is lots of orange. Some are more condensed than others. I'm guessing those are the older ones.

What do I do? I am NOT ready for more babies yet, but if they've already started growing I'm not going to stop the little things. Somebody please help!

 

[CelticOaksFarm]

If you don't see veins when you candle you don't have fertile and growing eggs.

 

[NHimport]

Ok... Most of what I see are what look like 2 air sacks - one on each end, and the one at the blunt end looks like it has a bullseye. They are very dark in the center. Only one egg had what looked like a "blob" 1/2 the size of a marble, looked like veins started. Can I put all the rest in the fridge? Are they ok to use?

 

[CelticOaksFarm]

Totally fine to use. Enjoy your ducks, be sure you dig in the hay every day as they love to bury them.