Hi there,
A healthy discus willl constantly be on the hunt for food and chances are they will eat just about anything that fits in their mouth (or at least have a good try at it).
I would stick with a meat based diet and try the occasional bit of the fruits and veg's you've mentioned. It will be a case of trial and error as to what the discus will actually take (if anything) and you must remove uneaten samples of food before pollution becomes an issue.
I only use 'Tetra Prima' (a commercial granular food designed for discus) and a variety of frozen foods (bloodworm, artemia etc) for all my discus.
Andrew