Neons, like all fish won't swim around much if they feel the tank decor isn't balanced it can even cause them, to sit there and do nothing, hover in one spot. Favore a spot, or cause them to stress.
Check to see if the decor, items and plants are arranged in a balanced natural manor. If you don't, have plants that are put in at a natural balance, then they will not swim, and favor the part of the tank, with the most cover. Or Hiding spots.