you can also coat your nori with garlic, as well as pellets--which are very absorbant and when you let them dry before feeding them, the garlic doesn't rinse off.
I had a blue tang that I bought as tiny for my first tank, a 25 gal, and it grew faster than I expected and I had to keep it in there a little longer than was comfortable. I put a huge powerhead in the front, pointing the length of the tank, which served as a tang-swimming-treadmill, and he loved it. But sometimes, after water changed, etc, I'd forget to turn it back on and he'd get a case of ich, twice so bad I thought I'd lose him. I got him through those epidodes feeding seaweed that I let garlic dry on (brightwell's is by far the BEST, and I've tried many), as well as pellets (make a small pool in the middle of a plate, pour some pelltets on it, then roll them around until all the garlic is absorbed, then roll the pellets to a dry part of the plate and let dry. With this method, they can be stored and used over a long period of time. I would make about 2-3 days worth at a time.)
Also, unless you're feeding a spirulina enriched brine (hikari makes an excellent one), then brine actually has very little nutritional value.
Finally, feed as many times a day as you can, BUT much smaller portions. That way, a fish that is fighting has a constant source of nutrition. Again, this is what I did with my blue tang, and he happily made it to a home in my 75 gallon tank.
Even without sickness, pellets are an excellent dietary supplement, as many are very high in protein (40-50%), are made with a variety of marine sources, and are fortified with important vit's such as C--which you can also get as a supplement for fish from brightwell. Actually, they have an excellent line, especially of fish nutrition products. I strongly recommend: Garlic, Vit C, Max Amino, and Amin Omega.
And no, I don't work for BW, but I have researched them extensively, and I really think Chris's products are miles above everybody else's. BTW, I used to work in a fish store, and successfully rehabed NUMEROUS fish that came in in very poor condition with a concoction of what I listed above--also feeding several times throughout the day. It works.
http://brightwellaquatics.com/
(click on enter, then products, then marine)
Good luck!