i have a few 6 discus with my rays and nooticed that one of the discus has developed a bit of a white film on his skin.is this normal or maybe fungus.the discus seems very healthy eats and is dominant of the group and still seems ok.How can i cure this.i do 10% water change everyday.i dont want to do meds because of the rays any body have cure or n-know if this is even a problem