Platies and mollies do not lay eggs, they are livebearers. Make sure you have both male and female fish of each species. Also be aware that when baby fish are born, the adults often will eat the babies unless the babies have plenty of plant cover (real or artificial) to hide in or unless you have a breeding box that allows the babies to drop into a different compartment as they are born so the mother cannot eat them.

Do you have males for these fish?