high voltage – Nixie Clock with Raspberry pi pico

I am trying to make a multifunctional nixie clock controlled with 2 raspberry pi picos. Because of my mistake I can’t plug every IN-12Bs into sockets. So I can only test a maximum of 4 at a time. After several tests, it was confirmed that all numbers were displayed in all digits.

Instead, I found two problems:

First, when testing 4 sockets, the edges of 7 or 5 did not light up properly.(blue circle in picture ). There was no problem when testing 3 sockets. I am using NCH6100HV to apply 170 voltage. This module can control voltage from 85 to 235 by turning variable resistance.

Second, K155ID1s(white circles in picture) are getting hotter and hotter when I apply voltages. I am using XL4015 Adjustable Voltage Stepper to apply 5v.

Could you help me to solve both problems? Also any advices to improve this thing are very much appreciated.