Presumed ammonia/nitrate problem?

You didn't cycle your tank first, so your fish may die because of the ammonia and nitrite/nitrate levels are spiked way to high. I would continue to do water changes (every day if you have to) and put in some (cycle) this will add bacteria to get it going quicker.(Or add live media from someone else's tank , like some gravel from the bottom) The fish are gulping at the top because the ammonia is high and they can't get any oxygen. If you have someone to give these fish to with an established tank, I would suggest it immediately until your tank is safe.