If these are tubes that haven't been used in a long time, they may have oxide build up on some of the pins (this includes tubes that have sat on distributor's shelves too).
Try cleaning the pins. A little tarnish remover, metal cleaning paste to shine them up a bit (you don't have to go crazy). If you have some Pro Gold, a little after polishing will hold off more oxidation from forming.
I use Mother's Aluminum and Mag Cleaner on Q tips I've cut down and put in my Dremel.
I've "saved" a lot of tubes that were headed for the circle bin with this.
In sensitve positions, you can knock off a few dB's of the kind of noise you described.