My Whitish Gray Female Zebra Finches

Question
QUESTION: I have established with you that I have two whitish gray females, correct?  So, when one day I discovered 2, then 3, then 6 eggs in their nest basket, I wondered who had laid them #1.  And #2, would they hatch?  And #3, which one had laid them.  I left them in the nest basket, even though neither of the two would have anything to do with the eggs, for about a week. I knew that they were not going to hatch.  My question is this;  I thought that they were only 14 weeks old?  And now wonder if I had bought older birds?  How old are they when they start to lay eggs?  Like I said before, the pet store was not very helpful, and by the looks of the place, not really concerned about the welfare of their charges.  Maybe a big part in why I bought the two poor looking birds in the first place.  Are there other ways to tell the age of a zebra finch female?  As soon as the eggs were laid, in a nest basket I might add, they wanted nothing to do with them what so ever.  I did capture them one at a time and marked one on the head with a purple food coloring, and the other with a red food coloring so I could determine which one of them was the egg layer.  Which made me think that they may very well be very young Zebra Finches. And the lying of the eggs indicated that they were mature, but really not ready.  With no male present, I can understand why they have not desire to be parents.  But, since I just probably answered my own questions, can you help me with trying to determine how old they are?

ANSWER: I'm sure you know that without males the eggs would be duds no matter if they sat on them or not. Females do sometimes lay eggs without males. It's rare in my experience but not unheard of.
Unfortunately there is no way to determine how old the babies are without leg bands. I can assure you that they aren't 14 weeks old. I have never heard of babies laying eggs that young. Most start laying after about six to eight months.
My advice to you is to see if the pet store you bought them from has any paperwork relating to them. Anyone with intelligence would write down when the babies were hatched or at least a rough date.

---------- FOLLOW-UP ----------

QUESTION: Thanks again, for yet another informative answer.  I did return to the pet store a few weeks ago, and asked why they did not band their birds.  AL I got was "We don't." and a blank look to bot. SO, if your answer is correct, than I have to at least one older Hen?  I did see a Cock in a Zebra Finch Book that looked exactly like the two I have. With no external markings of any kind on him except for the black line from his eye down his cheek, which is what my two birds have.  SO now I can maybe hope that one of my birds is a boy.  But, then again, I do not want to worry about baby birds and their care too.  I take very good care of any animal in my care.  From my Betta fish to my birds, to my doggy, I treat them as I would want to be treated.  With love, care and respect.  I will be near the pet shop this coming Friday, and intend to stop by and ask "AGAIN" about birth dates.  Don't think I will get an answer, though.  I live in the country, on the Texas Coast, and go to "town" {38 miles away]very rarely.  I did mark the birds, one with red and the other with purple food coloring, which has since been bathed off, to  tell which one of them was sitting on the nest.  But, since neither of them wanted anything to do with the eggs, at least I can tell them apart.  SO, I may have one of each, right?  Are females smaller than males?  I do not want to get into breeding of any kind what so ever.  But, know that the male has a prettier song than the female.  That's it.

Answer
You may. Another way to tell is to blow on their rear and see what types of feathers they have. Females will have no feathers around the rear and males will have long "feeler feathers".
This is not 100% accurate but it is usually right about 90% of the time. If you really want to know I suggest getting them DNA checked by a vet. Normally this doesn't cost too much.