What is on my tang?

[StephLionfish]

OK, so I have a 5 (?) inch Lopezi Tang. The other day I was staring into my tank, and I saw something on him. It doesn't look like ich or HLLE, and it's difficult to describe. You know when you have tanned or dry skin, and you run your fingernail along it, how it leaves a white-ish trail? That's what it looks like on the fish, only its a patch, not a line. A quarter sized ( more or less) patch across his right side on his face, and two smaller patches on his right side on the body.
The Lopezi swims normally, eats like a pig ( so that's normal ), isn't scratching or "sneezing". In the tank with him is a dwarf Fuzzy Lionfish and a dwarf Half-Black Angelfish. The lionfish hasn't messed with him, and neither has the angel. I feed once or twice a day, every day. Foods ranging from Brine, Mysis, Krill, Nori/seaweed(for snacks), Formula 1, Formula 2, some seaweed flakes, and I soak it all in Garlic extract. They also get some Macroalgae.

Ph-8.4 (Mm, I know)
Ammonia-0
Nitrite-0
Nitrate-40 ( I know, I know. I'm battling hard:uzi

VERY friendly fish! Oh and I only added him a week and a half ago. Please help!

 

[MrTuskfish]

Any way you could post a pic? I haven't a clue. BTW, is this a reef or FOWLR tank?

 

[stingythingy45]

Alk?

 

[StephLionfish]

It's..got some xenia and mushrooms in it.. but not much. I'm sorry. The pictures are on my phone ( I don't have a card for my camera) and when I tried to post any picture at all..it won't let me. I will try from my phone. See how that works. I'm also sorry, but I dont have a test kit for anything other than the ones I mentioned. It is my next purchase!