Why isn't the plaster drying well.?

We are changing the trim in the living room to a smaller width then before. And around the new windows the new trim is smaller as well and the wall was damaged when the previous trim was removed. After taking the cocking off from the walls and mold. I plastered all the trim edges to even out the paint and behind where the trim was before. Some spots were deaper then others and I just did one coat. I did this on Thursday and now it's Sunday and some spots are still darker then others like they didn't dry fully yet. ON the box it said that it should be dry in 60 -90 minutes and fully in 24 hours. So why is it still darker at some spots and how long before I can apply the second coat?