I think it's fairly normal for the quality of the egg to decrease a bit through the laying season. Full time laying takes a toll on them. From what I've heard, the spots are just a hiccup in the last spray paint layer. Is she starting to molt? My blue/green layers and Welsummer all had brighter, darker eggs in the spring and all got pale and lighter as the summer progressed. Sometimes those odd eggs don't have a proper coating of bloom on them, so you may want to pop it in the 'frige.