Are any of these fertile?

[Heatherwicz]

I have a few eggs, and this is my first time hatching so I’m curious if anyone would be able to tell me if these four day old eggs are fertile or duds! Or even any tips or tricks for knowing which is still a good egg or not

 

[The Happster]

Looking closely, they all look fertile.
I see veins in them all. Some are harder to spot, but definitely there.
Looking good!

 

[em_dawson]

Like OneHappyRooster said, they all seem to be developing. Good for you!