This is the power supply Maxspect lists..
Meanwell lrs-350-36
I always start there.. unless ther is lens browning or any noticeable (not easy) dimming.
But in your case I'd guess the leds themselves.
The wings are suspect with all the violets after 8 years.
Now if you tell me you ran them at no channel >50% then I'd go to the power supply.
Or if it was in an enclosed hot humid environment with little air exchange.