will platies kill a molly?

Question
in my 20 gallon tank I had 3 female platies, 2 male platies, and 1 male molly.

Well a week ago one of my female platies was dead.

Yesterday morning, my molly's half-eaten carcass was stuck to the filter.

Did my platies kill my female platy then kill my molly?? :(

Answer
Most likely if anyone is going to be picked on with what you have told me would actually be the platies. With mollies and platies being livebearers I always recommend to add some aquarium salt, they thrive much better with this added to the tank. In regards to the half eaten molly, once a fish is dead most fish will begin to consume the dead one. Were there any signs on the bodies of illness? If you have a bottom feeder that would have gotten to your dead molly first.