I ordered what turned out to be poor quality capacitors from...Amazon.
6 of the 12 failed. The failure was increased dissipation and reduced capacitance. These are 20kV capacitors failing at about 4kV. If I had read the reviews I would have saw they fail at low voltages. I used the caps in a tripler, the caps that failed were the caps that passed all the current flow, not the filter caps on the output. I have returned the first 12. I had order a second batch when I only had one defective capacitor, now I'm wondering If using them as filter capacitors on the output is less hard on them, i.e. will the have a longer life as a filter, then when passing all the current. Mikek