Hmmm,

28 days gestation period is just an estimation. Some females have their or biological rhythm they followed. Even with my keen eyes, some I expected to deliver by a weeks or so could translate into weeks even months. I noticed that females would be able to delay birth if the conditions are unfavorable Therefore the best method still to look for 'squarish belly' the experts talked about. Never failed me yet....

Sometimes female do drop a little brood maybe due to different fertilisation period as females are known to store few batches of sperms. So sometimes you might think they dropped prematurely but in actual fact thats a real drop.

Canibalism among females are common especially red eyed guppies since they can't differentiate between fries and food. But it can be trained. My females don't prey on the fries after a few drops