Is My Plattie Pregnant?

I'm quite a newbie at fish keeping if someone could help please?
I have a community tank with 7 neon and 4 rummynose tetras 1 bristlenose pleco and 4 redwag platties.
Over the course of about a week or so I have noticed 2 if my redwags getting fatter however only one of them is hiding in the plants if anyone goes near she chases them away( I'm presuming she's a she anyway) here are two pics of them I've been told to look for a gravid spot, what is this on the underside of the first one? Thank you for any replies

Yes, that's a female, and she looks pregnant (most female livebearers are pregnant all the time!), but she has a week or two to go yet before she gives birth.

These are two separate fish does that mean they are both pregnant thank you for your reply

I've just looked at them and seems I have a ratio of 1:3 and all females look pregnant. How long after the babies are born can I keep them in the breeder tank? And will I need 3 separate tanks for each female.

You can assume that all female livebearers are pregnant all the time; they are very prolific!
 
Forget about the gravid spot; look at the shape. Your first female has at least a couple of weeks yet, the second one is fairly close to giving birth; see how 'square' her belly is underneath?
 
I would just leave them be, in the main tank. If you want to keep some of the fry, then just make sure you have plenty of hiding places for them in the tank; fine leaved plants, like cabomba or Java moss are good for that.