As fat as that purple looks in the pic I'd say he is definitely feeding well. That's definitely a plus IMO. If you can get them to feed they will often pull through. Its when they seem to get lazy and lethargic and are not feeding that they seem to go fast.
If there is a plus to this situation, as Richard said, your other fish are get getting the equivalent of a vaccination against Ich. That's how vaccinations work, you expose the organism to a disease, or something like it, and they develop an immune response to the disease. The next time they see the disease, they recognize it faster and their immune system responds more quickly and the disease organisms are killed before it develops into a full blown outbreak. Its when their immune systems are compromised due to stress or malnutrition that the disease takes its toll. Richard's comments about temp. swings are an example of this. Just another type of stress. I have been dealing with that earlier this week and have been nervously watching for the first signs of Ich. That is also why I have never been a big fan of cutting back on feeding as a way to control nutrients. If you only look at it from a cost standpoint, phosphate remover or a refugium is a lot cheaper then replacing dead fish.
Gary
125 SPS, 75 gal. LPS/softie reef, 9 gal. Nano