There are two board images of a conformally coated Engine Control Unit at:

https://www.flickr.com/photos/128859641@N02/25836586336/in/dateposted-public/

Not the best images, but would anyone care to speculate on the composition 
of the star-burst patterns circled there?

Base on an even fuzzier image, I'd speculated that it was dye concentration in 
an uneven curing process, but these give it a colour that suggests external 
contamination of some kind, possibly bleeding into cracks.

The spikiness suggests a dendrite growth, but I don't want to get anyone excited.

RL