After you said you had blue arcing in the neck of the tube that is worrysome.If you disconnected the tripler it would have removed the high voltage from the tube therefore it would have stopped the arcing.Just for a test reconnect it and unplug the socket from the CRT.If you hear high voltage arc from the neck or can bring a grounded screwdriver(preferably a long one to keep your hand away from it near the pins and draw an arc your crt has aired)
If you don't get an arc maybe the tripler was arcing and putting too much focus voltage on the tube.If you hear the tripler arcing then that was the case.
Just curious if the 4 lead safety cap is an orange one or not.If it's got the old white one then it probably failed and took the crt with it.Better make sure your CRT is ok before purchasing a tripler.