Most likely your molly gave birth, there babies are black all over where as platies are usually yellow or in your case orange.
Just feed them crushed up flake or a product called Liquid fry food plus, it's flake food but in a fine powder. You might want to get a mesh breeding net they cost about £2 these are better than the plastic box breeders that float, these nets just clip over the side of the tank and prevent your icckle fishies from being eaten.
Goodluck
Keep an eye on water chemistry ie. ammonia and nitrite
Bigfish