1. You could add a series carbon comp resistor, 1/2 watt, to the bright cap
to pad it down. Try 220k or 360k.
2. Going into pin 7 of tube V4 is a 3.3m resistor with a 10pf across it.
You can clip a leg of this cap or pad it with a series resistor (470k or 1m).
3. Any combination of the above.