Good luck with the fry, Realkrafty! Very pretty fish. I have some 24k/gold dust mollies, and very few fry ever live. In the two or so years I've had them, I think 3-4 actually reached adulthood. Right now I have a few in my 10 gallon growout tank, but the adult fish and female betta usually get to them before I can get a chance to save them.
Ladydelaware, there could be all sorts of reasons for your fish loss. The first thing you should do is test your water parameters, do you have a liquid test kit? They are generally more reliable than strips. Since you just changed your filter, you might be re-cycling your tank all over again, with possibly an ammonia spike. Also, a bloated fish could indicate parasites, or possibly a pregnancy gone bad, so many possibilities. So the first thing to do is test the water and work from there. Welcome to the forum.