Have D1 Mini, using GPIO2 to 1st WS2812, which then daisy chains to another 3 (4 in total).
Powered externally from 5.5V PSU with a ground run to D1 Mini.
First two 8x8 panels are addressable and work fine, 3rd and 4th show a single white LED in the corner.
Have set LED Preferences to 256 LEDs and turned off “Enable automatic brightness limiter”.
Thanks for the suggestion. Have added +/- from the far end back to the PSU but still the same.
It’s a 30V/10A PSU that I’ve set to 5.5V/max amps (I assume it draws what it needs).
This was going to be my next suggestion.
-Desolder your data from Matrix1 and move it to the input of the 3rd matrix and see if 3 and 4 then light up. No need to change the LED count in WLED.