Too late to add a new one to the tank. If you want a third female, just keep one of the female babies in the tank thru adulthood. She will breed with Dad without any issues.
I have never had a headless baby just laying around. with each birth there will normally be one or two babies that doesn't make it... either born dead, or the mom thinks its not healthy enough. they get eaten.
[QUOTE=frankykeno;850310]Pull the dead ones. QUOTE]
I disagree. It is gross I know but, leave the dead ones. They will get eaten. Very good for the momma. Plus going into the tank at that point is just asking for trouble (posssibly more dead babies)