IMO, probably one of two things. 1) The isomalt wasn’t heated to a high enough temperature, 2) high humidity/moisture in the air.
What kind of “glue” did you use to attach the isomalt pieces to the cake?
When possible, I try to make my isomalt pieces the day of delivery. Or, if I make them in advance, I’ll keep them in an airtight container with dessicant and add them to the cake at the last minute.
Peace, Diane http://www.facebook.com/CakeDiane
