I would definitely replace those tubes even if it is not the source of your hum. You will greatly improve your enjoyment going with different brands. Both of those brands you mention make very poor sounding tubes in my humble opinion. Call Andy at Vintage Tubes services as he will be able to recommend the brands for the sound quality traits you desire.
Tube Question
I have an amp that has Russian Tubes. This amp purchased in the 90's has always had a hum to it which when playing music isn't heard. I'm thinking of buying 1 6SL7 and 1 6550EH tube to swap out and see if I can find if one of the tubes is the problem. The 6SL7 is Sovtek and the 6550EH is electro-harmonix. Should I replace with a similar tube from another company or continue with the same company? Is this approach to finding the problem sensible or a waste of time?