It is indeed hard to tell using a picture. I feed my mollies once a day on mostly vegetable matter, spirulina flakes, and find that they usually do not get to an excessive size due to eating too much. They do indeed square off as they should and are in robust enough good health to easily start to carry fry again. You need to find that fine balance between feeding so much your fish look overfed but still providing enough food to keep the fish in top physical condition. It can indeed be difficult to reach that point but I feed generously once a day and the fish are about done with the food they get and looking for more in about 2 minutes. That means they are getting plenty but not so much as to harm them by causing problems with swim bladders.