Judging by the picture it looks to be a female, the fish in the back I cannot tell very well.
Gestation period for livebearers is generally 28 days. And as the pregnancy progresses she will become very gravid and square off.
A gravid spot is a dark spot located near the anal fin and it will become darker over time this is where the fry are located.
To square off is a term often used around here
what it basically is - is the shape the female will take as she gets closer to dropping. Instead of having a round belly, when she comes closer to labor it will look square almost boxy looking
Now this is of a guppy but its the same concept. Notice how she looks more squared than the normal round look? This is what you want to look for
Good luck! Oh and of course,
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