Sick fish Please help

[DangerClose]

Hey Guys

Please can anyone tell me what is up with my tang?
I have been treating for Ich, pretty sure thats what it is, just double checking. I cannot isolate or remove the fish from the tank.
My tank is a few weeks old and right at the start of the ugly phase, I added a this tang and a small 6 line.
Over the last week I have notice a decent jump in nitrite, (2-5ppm). guessing my tank is going through another cycle as the tang and wrasse more than doubled the bio-load due to their size
All my other fish seem happy and all the fish are eating.
I am not noticing any out of the ordinary behavior (Not scratching on rocks or heavy breathing...ect)

 

[Spare time]

Can you post some pictures or a video under white light?

Are there any inverts in the tank?

 

[EeyoreIsMySpiritAnimal]

A few red flags:
"My tank is a few weeks old..."
"All my other fish..."

Without pictures it's impossible to tell what's wrong with your tang, but it seems like you're moving WAY too fast adding livestock.

Also, please consider a quarantine tank.