Was it always that light in color?
It's severely bleached.
I would squirt mysis towards it a couple times a week to try to bring it back to natural color and health, no large pieces of food, that takes energy, stresses it when this weak.
I don't give up until it looks like it's about to mush, but if still attached that usually is a good sign.
While light is their main source, it lacks the zooxanthellae it needs to produce light into energy, maybe why it's shifting spots, it wants light, it just can't do much w/ it right now.