1960-1970 Vintage Blue J.C. Penny V-Neck Sheer Sleeve Long Dress Gown Fashion

Was my MILs bridesmaids dress many moons ago. JCPenny, size 16. Please see measurements in my pictures. There are some yellowing spots near the hips/waist area, I included some pictures of this area. There were also some small yellow/brown, much smaller spots closer to the bottom of the front and one I noticed inside the bottom of the dress. They are all untreated.