The endlers you have develop a gravid spot very young, but they are now old enough to be pregnant. They probably are since they've been kept in the same tank with males since they were born. As they get near to dropping fry, their bodies will get deeper (back to belly). Their behaviour will also change a bit, for instance mine take to sitting on top of the filter. Don't expect too many fry at first as they are still quite young, they'll have more as they get older.
Are they still in with the platies as you said in an earlier thread? Although the endlers tend not to eat their fry, I wouldn't put it past the platies so if they are born in the tank, you may not find any!