The four fry probably belong to the one with the now-flat belly. She would have had around thirty or so fry. Usually, most of the fry get eaten.
If you want to save the fry from the gold one, you should move her to a breeder box. Just make sure to take her out of the box as soon as she has finished giving birth because she will eat the fry immediately after.
Remember, you are going to have about thirty fry, so either have a store you can bring them to, or make sure you have enough room in your tank.
The babies don't have to be in the breeder box for long. When they're born, they can't immediately swim. They just sink to the bottom of the tank. It takes about a day for them to be able to swim, and then they don't need to be in the breeder box. They can swim fast enough to avoid being eaten. If you really want to be sure they will survive though, you can keep the fry in there longer.
Good luck!