If are experiencing banana flavors it is not necessarily an "off" flavor if you are using a Belgian Ale yeast. Some banana flavor is desirable in Belgian ales, and the yeast strain will provide it. Cloves and spices are other flavors you can get from different strains of belgian yeast.
If you are concerned about which flavors should or should not be there, google the yeast that you used and see what the profile of it is. If you are using White's or Wyeast, both have excellent info on their site.