Hi there, I am kind of new to using marshmellow fondant and had a couple questions... i made cupcake toppers out of marshmellow fondant, left them out overnight covered, and when i woke up the next morning the fondant seemed very soft and sticky, almost like it was 'melting'.....  just wondering how to get the fondant to keep the same shape and texture it was when i first put them on the cupcakes.  Thanks!!!! :)

sounds like they were left somewhere either hot or humid? I would try kneading in more icing sugar before shaping them. Also ensuring they are left somewhere cool and dry when finished. 

I think you should not have covered them. They need to air dry to harden. HTH