I do 40%-50% water change in my Discus Juveniles tank everyday. I was told by many experienced discus breeders that Discus grow faster and bigger with daily water changes. I believe this is true because my discus are bigger than their siblings at petshop.
But you have to be careful about these water changes because Discus fish are highly sensitive to waster condition and would die if anything goes wrong. Also be careful about using Anti chlorine. Better not using it directly in yr fish tank. always better if you can have a separate tank or barrel to keep water 24 hours before put it in your tank.