If your pH is 6 I might think that the water is too soft for live bearers. I don't know what the specs are but they need hard water which usually brings a higher pH with it. Having ammonia is not good either of course, it should be zero.
What is your water hardness, GH and KH?
How old is the tank? Live plants or not? (Actually, I looked and you list no plants)
Water change routine?
Jeff
What is your water hardness, GH and KH?
How old is the tank? Live plants or not? (Actually, I looked and you list no plants)
Water change routine?
Jeff