Babies are Dying!!

Hello. I have 2 leopard geckos and I have never posted in the dragon forums. I am posting on behalf of my sister. My sister is breeding a pair of bearded dragons and has several successful clutches. The current clutch is currently presenting issues.

-The babies are eating well.
-The tanks are clean and have been sanitized.
-The babies are not growing.
-The babies are dying.

When I went over to see the tanks for myself there was one thing that I noticed that could be a potential problem. There is a dragon that is 6 months old, in its own tank that sits next to the tanks that the babies are in. I know that this would stress out other species of herps to the point that they die, especially chameleons. I told them to put a divider between the tanks so they cannot see eachother. Other then that I could see no other issues.

Any ideas or suggestions are welcome, thanks.

Michael, I'm sorry your sister's baby beardies are dying. She obviously knows the basics if she has raised prior successful clutches.
I do have a couple questions: What are y'all feeding the babies and where is the food coming from? And, last time the cage was sanitized, what did y'all use to disinfect?
Also, tell about the temp regulation you use.
I hope that together with others that post also, we can find the reason for the deaths and prevent more from happening.

The divider is a good idea. You could also put paper over the entire tank so they can't see anything. The less stress the better.

Also, are the tanks small and over crowded??? Is the heating correct??? What substrate are they on??? What are they being fed and how often?

Thanks for responding!!!
-The tanks are 20 gallons, with no more then 6 per tank.
-The dragons are eating pin head crickets twice a day. They buy their crickets from LLLReptile.com.
-No under-tank heaters, only lights. I don't know what temperature they have the tanks at.
-Paper towel substrate. There are also egg cartons placed at an angle inside their tanks.

Also, my sister seems to think that this could be a genetic issue???

2 suggestions:
Make sure the light is well to one side making a gradient. This is summer, and perhaps the light and hot weather is making the environment too hot.
I really recommend a thermometer, if they can't afford a fancy one just get a cheap one for now.
Also, just to be safe, I would wash out the tanks with something mild just in case there were traces of some chemical or disinfectant left inside. Good luck and please keep updating us.

Another thing to consider is the female's health throughout her laying cycle. Sometimes a mom will exhaust herself and her appetite will diminish while she is carrying consecutive/later clutches. If she wasn't eating as well and didn't receive the proper nutrition - it is possible that the embryos did not get the very best start before the physical incubation began.