How did you acclimate her to the tank? Drip or ?
Sudden changes to different water paramters can cause stress (breeders and your tank), and a drip method to acclimatize normally does the trick (this is what I do).
Do daily water changes and add a bit of epsom salt (my personal experience with salt and rays has always been good). Probably should turn off the wave maker as well
I had her in the bag for 30 minutes floating, opened the back and added a table spoon of tank water every 1 min for the next 15 min then released her in the tank, for the first 2 days there were no signs of the peeling white skin, this just started today when i got home from work i noticed it.