re: Candy making question

A couple things could have happened—you can have overheated the chocolate when melting, which can cause it to separate, become chalky/grainy, and often taste scorched.
Sometimes, chocolate will separate/seize if water is added; were any of your utensils or bowls wet/damp?

Finally, you might be using a chocolate especially poorly suited to remelting. Some chocolates easily go out of temper & look dull after melting, unless you’re properly stirring (the cocoa butter crystals become mis-aligned). That would account for a dull, ugly finish, but not necessarily an oily separation.