Internal pip is when you candle them a day or two before they are due to hatch and you can see the bill has broken through the membrane and is in the air pocket of the egg. From there, they then pip the shell (external pip)
If they are all from those dates, even if placed in the incubator one day after each other, they should all hatch around the same day. Which would make them roughly 3 weeks old. You've got another week before they are due to hatch!
When you candle them, you should see mostly dark egg (where the baby is growing), an air pocket or empty space at the fat end of the egg, and maybe some veining around the end of the air pocket and where the baby is. You should also be able to see movement if they are still alive and growing
If they are all from those dates, even if placed in the incubator one day after each other, they should all hatch around the same day. Which would make them roughly 3 weeks old. You've got another week before they are due to hatch!
When you candle them, you should see mostly dark egg (where the baby is growing), an air pocket or empty space at the fat end of the egg, and maybe some veining around the end of the air pocket and where the baby is. You should also be able to see movement if they are still alive and growing