If you discus had white waste it could have been internal parasites. If no other discus show sign of white waste then they might not have the problem. Just keep an eye on them. Watch to see if they are scratching on objects because this might also be an indication of internal parasites.
I have had my discus eyes get cloudy or have white spots. This could be a bacterial problem. What you could start with is a water change and some salt.
Follow the instruction for how much salt to add per gallon from the aquarium salt package. Sometime without using antibiotics I have had good results from frequent water changes and salt for cloudy eyes.
If you can post come pictures that could help.