Did you try just replacing the stock rectifier with a new stock rectifier?
No. But I did that across two systems with same result. I compared stock recti (allnic h3000) to half priced zesto and the zesto won. I was critical of Allnic on the forums, and Myles suggested rolling rectis. When I first visited UK Paul he too had the same Allnic with stock recti, and I didn't like his system with that, while with my Lampi it was sounding delightful. Realizing the Lampi uses the 5u4g recti too (mine is the KR) I put that on to the Allnic and bam, magic. Realized Dcc is also using that with his Allnic.
So I went back to the first place of zesto compare with the KR recti and not only does the Allnic sound much better now, but he also has a twice priced Trulife, and the Allnic with the stock recti sounds worse than that while with the KR sounds better than that.
In both systems with the stock recti you get a prettiness to the highs and lack of bass/midbass, body and dynamics.
Rockitman etc also roll their rectis. I now understand that even the other tubes in the Allnic can be rolled.
The h5000 apart from the same rectifier uses my favorite tubes, the KR 242, as stock. You can also upgrade the diodes in it, as Albert Porter and babybear did. Know a guy who owns the 5000, Dartzeel, IO eclipse, thoress and NAT phonos and various carts and prefers the Allnic. Good enough data points for me.
I am sure Trulife and zesto might respond to valve rolling, but haven't tried that. Zesto for its price is quite a giant killer though