Having read your other posts I think that although there is a small chance he is blind the main issues you're seeing (white glaze/fungus, clamped fins, lack of responsiveness) is more likely to be down to ammonia poisoning cause the tank isn't cycled.
How many water changes have you done since getting the goldfish? I'd imagine that the ammonia is way off the charts right now. Where abouts are you based? My best suggestion would be to take both fish back along with a sample of water and ask the shop to test it for you (normally free, max charge around £1). Ask for the EXACT results (take a pen n paper to write it down). You may not want to take the fish back though, in which case you're stuck in a fish in cycle situation but you still need to get your water tested.
You will need a test kit in the long run so I'd suggest getting one now, don't get paper strips if you do get one. Get a liquid based kit such as the API Master Test kit.
Then read the info on here about a fish in cycle.