The blackface tone stack is pretty bass heavy to begin with. Many people run with the bass control on 2. To get away from this you need some HF lift in a couple of places. Try a little bass cut by reducing one of the coupling caps. That .1 driving the mid network or the .022 driving the effects loop.
Are you really using 15K for the cathode of V1a? That's going to choke off the cathode follower V1b. The CF can't deal with too high a plate Voltage on the preceding stage. Not much signal can get through and what does will have ugly distortion.