It's hard to say what the issue is but it's hard to treat discus in a planted tank. I would start by increasing your water changes. If you can't do them every day then try doing 50% per water change. This could be flukes or it could be bioload.
Read this thread to give you an idea why planted tanks and juvenile discus require more maintenance than bare bottom tanks. http://forum.simplydiscus.com/showth...-Are-Important