a few baby finch questions

Question
I have four Zebra babies in my clutch, two have all white bodies with grey heads and two are all grey. Can you tell from this which are male and which are female? I am thinking this means two will be male, two female and when the babies are old enough I would like to put all the females in one cage and all the males in another, thinking i have 3 of each including the parents. Do you think this will work out, will the parents be ok being separated after raising a clutch together? They seem to be annoyed lately with each other, chasing around the cage a lot. The cages are next to each other, will that cause a problem?

Answer
1. You can not tell the gender, aside from DNA sexing, until after the first molt when the baby feathers are lost and the adult feathers are grown in.
2. I would keep the pair together. Many species of finches mate for life.
3. I doubt that is the cause, though at this point can not say what the problem is