Swordtail Pregnancy

[Tyler153]

Hi,
when i bought my 4 sword-tails (1 male) about two or three months ago one was pregnant and gave birth successfully (even though all the fry got eaten as there wasn't sufficient places to hide at the time) however i have not had any more fry since and i don't believe any of them even appear to be pregnant. my questions is why not and what can i do to help them out?

 

[Dieses Madchen]

I am sure they have probably spawned a couple of times, with no survivors. Mine spawn all the time. I just do not intervene. So I never see the fry,