Ick question

[Bob I]

I apologise in advance for this question, but since I have not had ick in my tanks for years I should be forgiven for not knowing much about the subject. As I mentioned in another post I bought a Yellow Eye Tang on March 7th. To make a long story short it came down with ick two weeks later. Two other fish also became infected, a Royal Grama, and a Bicolor Blenny. The Mandarin, Tomato Clown, and the six line wrasse are clear.
I don't need any opinions on what I did wrong as I am fully aware of that. I do have this question, however, The aforementioned fish have spots in the evening with the Royal Grama seeming to be bothered the most. He scratches and hides. The tang does not seem to be bothered much. It appears he is used to this.
By morning the affected fish are free of spots. Sunlight shines on the tank, and I see no spots. This gives them a chance to have a nice meal before the spots reappear in the early evening.
Do those of you who have a lot of experience with this have similar experiences , and most importantly should I leave it alone, or tear the tank apart to catch the Tang