Painted taillight housings, edges turned grey/white GRRRRRRRR anyone??

I took off my lenses today to put on a new pair, freshened up the insides with a coat of chrome paint, then masked it all off to spray the outside of the housings with black trim paint and the edges of the housings turned a greyish white, WTF? Any suggestions? I scuffed the housings lightly and cleaned them with wax and grease remover befor paint