sick mollies and guppies

Question
I've recently lost a molly and two guppies.  The molly (new to the tank) developed dull body slime.  One guppy did the same.  The other guppy developed a diffuse white dot.  All seemed tired, went to the bottom, and had trouble swimming.  Their appetite was off as well.  
Any ideas on how do I treat my tank?
Also I have a fun African dwarf frog (seems unaffected) that we want to keep safe from hard medications.
Thanks for your help!
Brad

Answer
Hi Brad,
Most medications are harmful to frogs because their skin absorbs it. If you want to treat your tank you would have to remove the frog to a quarantine tank whilst treating your main tank. If your fish had slime disease then a salt bath would be a good treatment. Add 1 teaspoon per two and a half gallons.

Regards,
Chloe.