I've had a clown do this before and it eventually faded in health and passed away.

I think the only thing you can do if your parameters are normal is to hope for the best and maybe feed twice as often and skim twice as wet. I would also dose garlic extract during feeding to entice feeding.

Is she ILL due to other clowns in the tank? Are these the only two? She could be stressed from other clowns and competing. Sounds like she can't find a good spot to call home due to competition taking the prime Real-estate.

Good luck.