WOW!!!! After an overnight soak the mildew stains are gone and the berth cushion looks brand new! I found a link to the IOSSO mold and mildew stain remover at snapfastener.com. I bought some at $33.40 (with "free shipping")for 12 ounces, figuring it's expensive but if I can save my cushions it was worth the chance. Instructions say 15 minutes, which did nothing, but it said for tough stains soak over night. I am very impressed with the results, as there were some pretty tough mildew spots.
I did, however, find a link direct to the manufacturer and it is only $19.00 including shipping, but I'll call next week and see if it's available anyplace locally.
http://iosso.com/products.htm
I wonder if any of their boat cleaning products are as impressive.