help! sick hippo tang

I have had a hippo tang for about a year. A month ago I upgraded from a 90 gallon to a 225. She was doing good then after about a week she got ich. I couldn't catch her to put in quarantine so I treated the thank with herbtana. No more ich but now she is hiding and not eating. I have tried nori, mysis, brine, aquadine, and new life spectrum all soaked in garlic (fresh and extract) and selcon. Today when I came home she was out swimming so I put some aquadine in the tank right away, she ate one then spit it out and went back hidding the rocks again. She was looking thin and pale, paramaters are perfect nitrates are up to 5 ppm due to having to turn skimmer of for the treatment. What can I do? I really don't want to lose her. I did lose 3 clowns to brook but from my research it is supposed to only affect clown fish. The tang does have some scratches from when she had ich