Purple tang disease ID help please

[Cobrasvt1999]

Hello all! I came home from a break and found my purple tang isnt looking all that good. He is now in a quarantine tank and currently im debating what he might have. Any ideas? no new fish or new anything has been added to the system for about 3 or 4 months, making me wonder what could have caused this. Sorry the image is blurry. He didnt want to cooperate in getting a photo.

Symptoms beyond the visible are rapid breathing and decreased appetite. Normal otherwise

Thanks,
Lars

<a href="https://ibb.co/gT8nuw"><img src="https://preview.ibb.co/b43LEw/purple_tang.png" alt="purple_tang" border="0"></a>

 

[Cobrasvt1999]

Some more information:

1. How old is this aquarium?

4 months stable with live rock from 1 year old aquarium

2. If less than six months old, what is ammonia level?

0

3. What is SG of this aquarium? How measured?

35 ppt w/ refractomiter

4. When was the last fish added to this aquarium?

3-4 months

5. Was it quarantined? If so, how? And how long? Was it prophylactically treated? How?

This is a holding system after main is going sterile due to ich. no TTM yet, but upcoming

6. If you are using a copper based medication, which one? How often do you measure level? When?

N/A

7. If you are using hyposalinity, how did you calibrate your refractometer?

no hyposalinity, but refractometer calibrated with RO/DI water

8. Please describe in detail, the appearance of the fish? If there is one or more pimples, are they lumpy? What color?

See above

9. Please describe the behavior of the fish as best you can. Is it acting reclusive? Is it always up towards the top of the aquarium? Is it avoiding light? How active is the fish?

See above

10. Is the fish eating? What?

See above

Thanks again!
Lars