New eggs incubating (Day 4) and New eggs from Feb Chicks

We started a new batch of chicken eggs the other day.  We will soon be ending day 4 and starting on day 5 around 3:30 PM.  There are 19 eggs in this batch.  Six (6) of them are questionable because they are from our current chicks.  Since we know we have (2) roosters perhaps it is possible they are fertilized?  We're not sure.  We'll be able to candle them soon and see if there is anything growing inside of them. Here are the eggs before incubation.  I broke one by accident.

  Here they are in the incubator:

We have kept the temperature around 99.5.  Thus the thermometer fluctuates between 99 and 100 degrees.  The humidity fluctuates between 25-30%.


The chicks we hatched back in February are now around 15 weeks old.  We think we got 2 new eggs from them today.  They didn't look like our other eggs and they even had a somewhat rough shell texture.  They were also smaller then our other eggs.  A hen laying eggs at fifteen (15) weeks is early but not unlikely.  Hens usually lay eggs around 18-20 weeks.  That has been our experience in the past.

Here's a pic of the new eggs:

Here's a pic of one of the 'new' eggs next to one of our regular eggs.

 So what do you think?  Is it an egg from a new laying hen or one that is already established?