I've been making royal icing for years and never had a problem like this until the last few months. It seems like I get dark splotches on my cookies almost every time I make them now. The base coat dries for about 12 hours and then the splotches appear - mostly on the corners and edges. It looks almost like they are wet, but they're not.
I've tried changing meringue powders, baking the cookies longer, drying them with a fan, cleaning the bowl extra well to remove oil, but none of that has worked. I also thought it could be the humidity, but it happened in the winter a few times too so I don't think that's it. Any ideas???
Sweetjr, I have had that problem recently..I'm thinking maybe I didn't let cookies cool off completely before icing with RI. I usually let cookies cool for 1/2 day or overnite. This time, in a hurry I iced 1st coat within a couple hours.
You might be using too much color - we got that on our cookies, especially with red, blue, and purple - ones that need a LOT to make them vibrant. Cut back a smidge and see if that helps (and let your icing set for at least an hour to get to its full color)