I purchased some call duck eggs recently and they are only about 1 week in the incubator. I candled the eggs to track the development inside, all the eggs appear clear with many blood vessels that have formed inside. However, one egg in particular is extremely dark inside. The egg has a deep bluish glow inside but appears otherwise normal on the outside. It doesn't have a smell, so I don't thing its rotten. In fact, I can partially see some blood vessels that have developed despite its odd color. Any thoughts on what is up with this egg? I wonder if the seller accidentally mixed up the wrong egg with something else? Hopefully it will hatch.