Molly has swollen lips (new tank)

[Chimanihk]

We have a new tank set up for one week. It is a 15 gallon tank. I treated the water to remove chlorine and added beneficial bacteria for three days before adding fish. We added five fish (two mollies, two platies and one Swordtail) on Dec 28 and four neon tetra on dec 29. Two of the tetras have died and one molly has swollen lips and is not active. The others look fine. pH is fine, nitrite is almost zero, ammonia is .25 ppm. I did a 50% water change today and reduced feeding to one per day.