Strawberry Shortcake

Busy weekend - 1 of 3 cakes I made. I used Colescakes416 idea for the top border. Initially my icing looked fine, but when I let the fully iced cake sit overnight covered in saran wrap, I pulled off the wrap to see that the icing had developed little white spots. The color wasn't mixed well apparently, or either that dang salt I put in the icing was the culprit. Will we ever know what causes this?! I forgot to put the seed dots on the big strawberry. I fixed that before I delivered. Forgot to get pic!