Hi, I'm having problems with a new tank and am looking for help. I have lost 3 fish so far, and the other 3 don't look good, 1 gasping for air, the other 2 not eating only 1 playing like normal. The one that is gasping for air also appears to have finrot, visible damage to fins. Other fish are not attacking or nibbling at the fish. All 3 remaining fish are male guppies who have gotten along since I brought them home about 9 days ago. The 3 that died were 2 male guppies, and 1 Dalmatian molly all bought at the same store at the same time. All 3 died within a day of each other all from the same gasping for air and not eating symptoms. No visible damage to those 3. The tank is a new 20 gallon tank kit. I treated the water for chlorine, and added tetra safe start and let the tank run for a week before the fish we're purchased. The fish were fine for 2 days and the they started acting funny. The first one died 3 days later, 5 days after purchasing them. My tank is at 76 degrees, my ph is at 7.6, my ammonia levels vary daily between .5 and 1ppm, never above 1ppm when testing, 0 nitrite reading, and 5ppm nitrate reading with matches my tap water. I have been doing daily water changes of 4 gallons since I lost the first fish. I am aware of the nitrogen cycle. I am using a API freshwater master test kit, the liquid, not the strips, and my test match what petsmart got when they tested the sample I brought them. After reading multiple forum post and after talking to the sales associate at petsmart I decided that adding 3 tablespoons of aquarium salt would do no harm, and may help. I added that this afternoon. I was also told that my ammonia level was safe and shouldn't be killing my fish. The other advice I received from petsmart was that if I lost all the fish I should empty and clean the tank and start from scratch because it may be some disease. I have 2 questions. 1, Is there anything else I should do now to save my current fish. 2, If I lose all of them should I start clean, or continue cycling my current water. Thanks in advance.