Yes, mollies have a more rounded front but when they are pregnant, they get more rounded in the back as well. If they were ever with a male Molly or male Guppy, ( I see a male Guppy in your 2nd pic), the fish are either pregnant or holding sperm already. (If these are balloon Mollies, it will be harder to tell when they are about to give birth because they are misshaped fish so none of the usual rules apply to them. ) If you are looking for more baby Mollies, add a lot of frilly floating plants for the females to use for releasing their fry. If you are not looking for more babies, do nothing and when they give birth, the other fish will eat the fry.
When it comes to moving females, you do not want to move them when they are heavily pregnant so you'd want to move them a few days after they gave birth. ( Mollies do no parental things with their fry.) They will be weak from birthing so you don't want to move them too soon after birthing.
Hope this helps.