Issue with Network system

Looking for help

I am having trouble with networking 2 slave boards with a master using software serial. I am using a master board with a button that will send a 1 over serial; then the two slave boards will read the serial and turn on when the 1 is detected and send back a confirmation. I am using 2 ATtiny412 processors for my slave boards and a ATtiny1614 for my master. my hardware is working but I am confused on my code issues. I will post my code and

master board schematic

Hi!
You can follow this documentation

http://fabacademy.org/2020/labs/leon/students/adrian-torres/week14.html#hello_serial_bus