well i heard that the females can store enough sperm to give birth for a year

but now i have a diff question...she gave birth today and i took 6 out and left in 8 for population control...the 8 and the mother and 1 other female guppy were living peacefully...for atleast 5 or so hours and then 1 by 1 they start disapeering...why all of the sudden did the 2 femes eat the babies?