Usually, when the decorations crumble after drying, it is a sign of over-beating. The icing needs to be beaten at a slow speed for 7 – 10 minutes. If is beaten on a high speed, too much air is incorporated and results in crumbly decorations.
Because of the high humidity you mentioned your flowers will take longer to dry. Try adding an extra tablespoon of meringue powered to the recipe. You might also have to reduce the water a little.
Hope this helps. If not let me know and I see what else we can do to help you.
Cora
Cora Smith
Wilton Industries, Inc.
