10 NO3 is an indication that your tank has not matured (or something is causing the high NO3). As long as PO4 is zero, you can try to introduce a piece or two... but the high nutrient level in your tank may cause its colour to fade or "browning". But again... that's entirely subjective (and depending on luck also).
As far as possible, try to choose specimens without any damage... however if the colour looks fantastic and the price is right... no harm I guess