if growing from seed 4 females may be ideal for a 400 but even then it could easily become to overcrowded if you vegged them very long looks like some of your plants may be showing sex soon and maybe you can remove alot then.
when using seed you do not have much of a choice when using clones you can usually get the best yield by flowering more plants and keeping them small like using just rooted clones will keep the canopy more even and the 400would be able to more efficiently light each plant and your yield would be better than a using a few larger plants.