Is your hen with a male? (sounds silly but it is valid).
You said she laid 3 eggs but there is more in the picture, what are the others?
When did she lay the eggs? Is she sitting on them?
Also, if you candle the eggs too soon, they will appear ´´infertile´´. Recently, I candled my clutch after a week because there was 10 eggs. So obviously the hen (Aldora) had laid 2 clutches because, her last clutch hatched and I got Lapis and Nube. I had marked the eggs too. 1-4 were infertile. 5 I was unsure of. 6 7 and 8 had babies. 9 and 10 looked infertile, but i knew they were fresh. I tossed eggs 123and4 so that they would not impede the others.
My egg 5 never hatched, all the rest did. So best leave it be if you are unsure.
From the photo it is hard to tell, but if it is fertile you will see the red lines (veins) very clearly.