Help me please :( Angelfish not eating, water is perfect

Help, I dont know what else to do. About a week and a half ago I noticed one of my angelfish was not eating. At the time he was in a 30 gallon tank with another angel, 4 tiny tetras, 2 platys, and 2 small silver dollar fish. I have had the 2 angelfish for like 6 months, I got them as babies. I actually bought 4 baby angelfish at that time but 2 died right away of angelfish disease (they had clamped fins) and the 2 I have survived. Anyway the 2 I have, have never had anything wrong until about a week and a half ago I noticed he stopped eating. I let it go for a few days but then I noticed he was started gasping, or opening and closing his mouth much faster than usual. I went to my pet store and I told them whats happenning. They measured my water and told me that he has good news and bad news. The good news was that my water levels measured perfect. My PH is 7.5 and I keep the tank at 80-82 degrees. He said I am a great fish owner and I should continue to do what I am doing. The bad news was that my water levels are not whats causing the fish to be ill. This wouldve been easy to fix. The store had me move the fish to another tank (10 gallon) which I already had set up with water parameters same as the 30 gallon. He is still in there. for the first 4 days I was adding cure all and melafix to his tank, hoping that it would help. He seemed to be declining in strength. He was still gasping and not eating and at this point I noticed he was having long clear stringy feces coming from him. Also sometimes he was swimming at a very slight angle, sometimes with his head down. 3 days ago I read a million websites and his symptoms seemed to most closely match hexamita. So I found the cure to hexamita is a medicine called Metronidazole. The same day, I went to the pet store and bought it. They had me do a 50% water change to get rid of the cure all. Then I added it to the tank according to the instructions. Then waited 2 days (which brings me to today) and added it again, as it says to do in the directions (It wants you to add it every other day). Every day I put a few flakes of food and a few bloodworms in for him and sometimes he will go up top and I think hes going to eat but then he just goes back down and sits around. I am not sure if this is working or not. If it is working to kill the bacteria, I am afraid he might die from not eating. Is there anything else I can do???? Is there anything you think it might be???? Has anyone else had this problem???? I appreciate any help you can give.