Getting to know my gouache colors

Getting to know my gouache colors - student project

Getting to know my gouache colors - image 1 - student projectGetting to know my gouache colors - image 2 - student project
I am not quite sure why the nude and light blue color started to crack when dying. The dark blue was completely dry (over night) and I tried different techniques to get the opaque look, nevertheless it cracked. Any ideas how I can avoid that? 

Getting to know my gouache colors - image 3 - student project