These fish do take 5-6 weeks but some time it take a little longer but at 24 that about right for them.
The first way to sex is that young males gonopodium will start to devlope, the anal fin on the young males will start to thicken up.
At this stage i strat to remove the males to a different tank or a breeding trap.
This is to stop the males breeding with the young females and to get good sized fish.
However I seen many people keeping parents with fry and no splitting of the sexes and still getting wanderfully sized fish.
Back to the ratios, you allways have fry looking like females, and i wouls give then a few more weeks and you will get males poping up soon.
Helter