RX 480 fan/led pcb diagnostics - seeking help

[Cheap Charlie]

I’ve got 2 AMD RX 480 GPUs, recently the fans and logo led stoped functioning one one of the cards.
I’ve disassembled both cards and interchanged components to narrow down the source of the issue (fan/led PCB).
I’ve pulled out the multimeter probing component. I’ve found some anomalies comparing readings from the known good PCB, I am however at a loss to determine exactly which component is causing the fault.

Anomalies:
1) resistance between input negative and FAN 2 negative, bad board 0.5, good 29.7.
The same readings are achieved at Q1/2/3 across both boards.

The traces for the above appear to run back to R7/8/9 respectively.

Any advice on where to from here would be appreciated.

Note, the PCB at the top of screen (missing coating adjacent fan1 pins) is the faulty PCB.

[AmnevaR]

First rule of troubleshooting... Thou shalt check voltages 

[Cheap Charlie]

Thank you.
Where would you recommend I capture voltages at?
I’ve replaced a few failed caps and fuses on motherboards over the years, but this one has me a little stumped with the variation in resistance.

[AmnevaR]

As I understand the power to this board comes from the pin header on the right (second photo)?
I would measured what voltages comes to this pin header and then disconnected the board from graphics card and hook up a power supply to the pin header (with the same voltage and limited current if possible or just use jumper cables to the graphics card at your own risk).
And then I would measured what is the voltage in various points on the PCB. I see some voltage regulator 78... something and some 8 pin chip. Look up the datasheet for those parts and check what pins are connected to power, measure them.

Or maybe the problem lies somewhere else ... scratched track... cracked resistor?
This bloody black solder mask doesn't help either...