With a problem like this, always try fresh leading plugs. I don't thing the trailing plugs matter much, so I wouldn't bother with them.
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While the trailing plugs do not work as much as the leading they can get real wet and not fire at all. Tom, it sounds like one rotor is flooded and not firing at all. Is that the first time that you ran it after installing the plugs? Check your firing order also, make sure nothing is crossed.