Half of egg clear

[Runer]

Hi,
I'm new to keeping poultry. Recently I ordered hatching duck eggs and have been incubating them for 7 days. I've tried keeping the temp and humidity right. Now I candled them for the first time and am confused. I see blood vessels but half of the egg is clear colored from the middle. Shouldn't it be all the same color except the air cell on top? Couldn't find any examples of this on the net and worried.

 

[AltonaAcres]

Looks ok. Some of mine look like that and some don't. As the egg continues developing the veins will go all around the egg.

 

[BirdsBeesTrees]

Normal.