I am an avid feeder of my corals, but I would second the advice above. I have unfortunately had several acanthos die and I think that when they don’t eat they are not in the best of health and find it kind of stressful to eat. My experience with trying to continually feed them in response to them not eating is them dying. If you want to make it gets some nutrients other than from the light I would try turning your pumps off and giving it some liquid food like Restor.
Just another note, I do have a tang that really likes to steal anything I feed them so it’s possible they just don’t want to be harassed if you have something similar because I have seen the feeding response go down after the tangs pick at the food they have caught.