I just did a quick Google search for the Tetra pro food and I suspect that it is a poor food for mollies. It seems to be a food that is high in animal proteins, which would be a great food for carnivorous fish. A molly will do better with foods that are high in vegetable protein content instead. I have no idea what may be in the catfish sinkers, but if that is a high vegetable content pellet, it is probably a better food for the mollies. A quick search shows that Tetra also makes a vegetarian diet if you prefer their product line. That would probably be a good staple diet for the mollies. I find my mollies live for many years and I do not lose over half of them in a year. That kind of loss rate tells me that something about the arrangement is just not working. If all that you have in the tank is mollies, you can try to make sure that the mineral content of the water is high and the pH is also high. For domesticated mollies, people have known for some time that an easy way to get that condition is to add some sea salt to the tank. Do not add that salt if you have other fish with the mollies because most fish cannot tolerate the salt as easily as a molly does. In that case, you would need to work with something like crushed shell or crushed coral, the kind of thing that saltwater people use as a substrate. Those will slowly dissolve in your water and add hardness and raise the pH of the water all at once. Another factor that people sometimes get wrong with mollies is keeping their tanks too hot. Because we think of them as tropical fish, people will run their tanks at 26C or higher while a molly will often do best at 24C or even a bit lower.
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