Sad post

So after writing up my carpet disaster this morning, we have had at least four deaths in the rainbow tank, two Bosemani, one red and one dwarf neon. They have all happened today which is odd as the accident happened Saturday and it was Monday night that we moved the tank - it's been two days now and all stats are fine... 

I've done a water change and added an air stone but I'm at a bit of a loss at what else to do. I don't want to transfer the fish in case of disease. The remaining inhabitants look ok but then the Bosemani all looked ok when I went out two hours ago yet two have perished. I am hoping that there will be no more casualties but I'm baffled, what could it be? The only thing I can think of is a ph swing due to changing so much water at once when we had to refill the tank after it lost over 2/3 of it's water but that seems a bit out there as rainbows love big water changes so it wasn't more than double the usual change. The fish aren't showing any sign of disease or distress. They're coloured up (even post mortem, see sad photo!) and not gasping for air as you might expect. I'll do another bucket in half an hour and keep doing that.

I need wine.