[morzh]

OK, the tubes:

12J5
12SA7
50L6
35Z5


Now, the interesting thing: I have just come home and put two halves of that same cap to keep reforming, installing two 50K resistors to each half. One of them has been reformed since yesterday evening and through the nigh.
The thing is, the second half behaves as if it were reformed too - it has the same more or less leakage current and the difference between the two voltage drops across the two resistors is about 1V - 3V vs 4V or so. Right now (after 20 minutes) it is 3.3V vs 2.7V.

there should be some peculiarity of the way the cap is made that resulted in it.