As others have said, tubes are consumable. So there’s that and also different tubes have different sounds. After five years, I’d replace at least the output tubes and if you liked the tubes five years ago, then buy more of the same. But if you didn’t, try another company. And don’t go cheap! You get what you pay for.
Another thought. What time of day do you listen? I have had the exact same problem later in the evening, but not in the morning. Electric guitars, saxophone’s and women’s voices would hurt!
All the best.