ok first of all have you quarantined the new fish,not a good idea to put any new fish straight into a tank.anyway i do a 25% water change every 2 days on my 50 gallon with four discus in it,how often and how much of a water change was you doing before you added the new fish?
thanks for your reply no i didnt put them in quarantine he had them in shop for a week before they went on sale might be a mistake on my behalf i do a 25% water change ones a week on my tank been reading up and everyone says different about water changes
Need to do water changes more often no matter how many Discus you have. 2-3 times a week is fine, once a day will give you the best out of your fish.
On another note, you should really looking into your fish choices, you have some stocking issues. Discus should never go in a tank with Bala or Silver Dollars. These fish get big, and spook/stress the Discus with their fast movements. Not only that, they will out compete the Discus for food, guaranteed.