I dont want to sound rude, but if you had done your research, you would have known 5 gallons arent enough for any of the animals you have there, or would have know that having a
test kit is vital, or that whenever adding so many creatures at once in such a small space will most definately throw you into a mini cycle, which is most likely what killed your frog, not the mollie. You would have also known that people at the stores want your money, and will probably tell you a whale will in a 5 gallon just to sell it to you.
I am really sorry, we really tried to help you, but you never answered our questions.