They're not testing for trace minerals. Darth is right. You can't use distilled water for fish. You should be changing the water way more often, like twice a week. There should not be any ammonia at all. Use tap water with the water conditioner added instead. Try and match the temp of his water now so it causes less stress. All water conditioner does is remove harmful chlorine and other chemicals from tap water.
My recommendation would be to get him a larger space that can support a heater. He needs a contant warm temp. 80 would be ideal. With smaller containers their temp can flucuate a LOT and that leads to listless behavior and a slower metabolism. He could also be sick from ammonia. Clean, clean water, warmth and time.