300b valve/tube expectations

I have recently been attempting to make a final affordable improvement to my 300b system. I replaced my EH Gold Grids with Psvane 300B Black Bottle - T/2. I thought the overall sound quality improved from the start and after three weeks at around 4 hours a day playing I was very pleased indeed. But I did have a couple of concerns. The new valves were louder on standby than the near silent gold grids, but this could not be heard on play back, so OK. Second concern: there was sort of warming up tinks and plops for a couple of minutes [not amp dependent] . Again not on the Gold Grids. After a couple of weeks or so I realised the warming up sound was only emitted from one channel. A reversal of the valves located the noise to one of the valves. I reported this to Hotrox from where I had purchased the valves and was assured, so far as this didn't interfere with playback, there was probably no problem and the occurrence was not uncommon. I was reassured and proceeded, but after a couple of days, the noise became prolonged, 5 minutes or so, and then more aggressive, eventually occurring half way through a C.D. in a pretty explosive way, threatening my amp. or even speakers. I now await replacement for the matched pair.

I would be really grateful for any illumination on what variations to expect from valves. I have only converted to valves a year or so ago and only tried three pairs of valves. The Pasvane really were worth the 100% increase in cost, but for unwelcome side effects.