Milk spots are a bummer. It is my understanding that you can't get rid of them, but this is not my series. I don't know if PCGS has any gurantees on this stuff. I tend to doubt it, but you might ask.
I believe that the change in holder speeds up the spots. The proof half dollars in 1964 had the same problem. I understand the services can reduce the size of the spots but they will come back.