Thanks, Robin. I think you're right on that the frons killed them. I was under the impression that the frons were so very peaceful and wouldn't hurt the new peacocks. Well, to see mouths wide open on the little peacocks is a good indication that I was wrong. Even though I have rock caves along the entire back of the tank for territories and hiding places, I think that's probably what happened. I'm still confused as to why the survivors were gasping at the top of the tank with the only apparent oddity being the high nitrate reading.
I don't recall what the nitrate reading was, but the tank is empty now until I can get it corrected. The frons got moved into my 29g which I set up a while back to create another malawi tank. Now, I'll just have to wait . . .
I'm just very confused as to the cause of the whole thing. Thanks, again, and take care!