They all look I'm various stages of pregnancy in my experience. The two largest platies look farthest along imo, maybe a few days to a week and a half? The spotted Molly, she looks like mine when she is about 2 weeks from delivery.
When they get boxy and a waddle type, funny way of swimming, and the cloaca starts to protrude or descend a bit, and esp if they become secretive or aggressive all of. Sudden, that's when mine give birth.