Dying Mollies

Question
QUESTION: 3 days ago I bought 3 mollies ( different varieties) from my local pet store..within 5 hrs all three were dead...I took them back to the store today and they replaced them...now 4 hrs later they are all dead again...I did a water test and the only thing that came back slightly off was the PH...Ive got another Molly in the tank and its fine as well as 3 zebra fish..
Not sure if the problem is my tank or the petstore?

ANSWER: Elissa,
It would be safe to say the problem is with the pet store. If there is another in your town, try buying there and see how their fish are. Don't forget the Molly fish is a brackish fish and needs salt in the water.

---------- FOLLOW-UP ----------

QUESTION: So I went to another pet store and bought one more fish..and the same thing happened!?!? I just dont know what to do..the fish in the tank are just fine but the new fish die off within hours..
I have a bacteria treatment, should I try that?
BTW the fish seem to have white spots on them and the eyes turn whiteish as well..

Answer
I am wondering if both stores are using the same breeders. If there is a small family owned pet shop, I would try them. They usually go with different breeders because they can really afford to be replacing fish. If your fish are doing well and only the new ones are dying, I would say its the breeder.