Urgent urgently need I.D/help on this fish disease.

I just saw my powder brown tang go from looking fine to this in less than an hour. the white spotts are large and not round...it actually isn't white its yellow like the edge on the tangs fin. I don't know why or what is the cause my water checks out fine PLease Help!

 

google Oodinium and see if that looks similar.

 

close but no...they aren't dots they are like rounded diamonds....and now the spotts are gone. that pict was taken 15 mins ago and he looked like that. now they are gone??? something is very wrong i think..all i did was a very small water change maybe 5% between my last post and this one. it cant be my water everything looks fine on a test

 

well sometimes when a fish gets stressed out they get spots not bumps like ick but spots. Do you see any odd behavior? like scratching?
is it eating?

what are your water parameters?

 

I had been battling with ich for the last week and determined my hydrometer was no longer accurate and was likely the cause. i slowly brought my salinity down from 1.031 to now at 1.024 over the last week and all looked good. now this. you could be right though about it being stress cause all i have done is turned my lights off and changed out 5% and the spotts are gone. It freaked me out...he has been acting weird since the ich started..just alittle rubbing and swimming head on with a powerhead. it was fine when i fed it ,ate like a pig...10-15 mins later it looked all marked like in the picture. my parameters are : salinity 1.024, ph 8.2, temp 81 (bumped up from 78 to speed up the ich), nitrate 0ppm, ammonia was 0.25 before water change, didn't test cal or KH or phosphate but those were bang on 2 days ago and shouldn't be a factor i dont think

 

That .25 ammonia will make him stress and get ich like that.Might want to use a little amquel+ or another type of ionizer.Prime maybe.If you have montiporas try the amquel+
as montis dont deal well with prime.