Well you do need to know the sex of the plant before you call it a mother. There is no point in cloning a father. If you want to know if you have a mother or not then you take a few cuttings from each plant. Number them so you know where they came from. Once they root switch them all to 12/12 in a week or two you will know if you have a mother or father so now you can go back to the plant they came from and know if it's a mother or not.

The idea behind this is to keep the plants you want to use a mothers as stress free as possible. Just keep it in veg cycle until you know then you still have the growth time going forward and no stress to the plant.