Uri – it sounds like the Tone control’s “taper” is somehow ‘off’ on your build. Can you double-check the values of R8 & R9 as well? Short of that, have you considered trying an A100K (audio taper) or a C100K (reverse audio taper) pot for the Tone control? It might make the difference.
Also, some good clear photos of both sides of the finished PCB might prove helpful.
Oh, and this is the “Guides” section. Hopefully Barry will catch this and this thread to the appropriate “Build Support” section.