Neons dying one by one

Is pH killing my neons

About 2 months ago I had 6 neons. I have had them slowly die off one about every two weeks. Nitrates, nitrites, and ammonia have all been zero before and after the deaths. The wate temperature is a 78 degrees. The only thing I can think of is that my pH is killing them. It runs around 7.6 to 7.8. Could this be it? I am thinking of getting some RO water and adding it slowly to lower the pH over time if it will help.

I read things that say only the wild neons need low pH and that most captive bred ones should have no problem with it. Most of the fish I have prefer lower pH on most characteristic websites but as I have read many times, "these are guidelines, most fish should have no problems with a higher pH".

If there is something else I should check I will. I am down tothe last lone neon, but I do not want to get it any buddies if they are just going to up and die on me.

Ems said:

do they show any signs of discolouration or disease? either before or after they die?

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Nothing, their color is great and they show no signs of being ill in any way. I watch my tank for probably 30 minutes each day so I think I would notice odd behavior as if they were getting sick or something. They tend to die overnight so by the time I find them the are nibbled on by their tankmates so they do not look to good.

Tankmates are 2 blue rams, 1 guppy, 5 rasboras, 4 albino cories, 2 ottos and a few ghost shrimp in a 29 gallon tank. I have never seen any fish act agressive towards another other that the rams occasionally chasing each other.