Biocolored blenny turned paled, then died...Why?

[New&no clue]

As the title says I have had this blenny for a little over a year, with no issues. Last night I noticed he was face first into the hole he likes to hang out in with just his tail sticking out, odd behavior for him. Then later in the night I see him on the sand bed very pale and lost most of his color. I assumed he was dead at this point so I grabbed my tongs to pull him. Spoiler alert he was not dead and I nearly had a heart attack. I knew he was obviously having issues so I got him out of my DT and into my QT. While trying to find out what to treat him for, he passed.

I'm now concerned for my other fish. Did he turn pale because he was dying, or is the loss of color an indicator of something else? Everyone else in the tank is fine, so far. Parameters from last night

Ammonia- 0
Nitrate- 15
Phosphate- .1
Calcium- 430
Mag- 1450
Alk- 7.5
Temp- 78, but has been getting up to 80 during the day

 

[Jay Hemdal Verified Community Expert]

What other fish do you have in the tank, and when was the last fish you added?
Was the blenny skinny? It looks like it in the photo, but I couldn’t tell for certain....

Jay

 

[New&no clue]

I have two clowns, a purple fire fish, a coral beauty, a yellow tang, and a mandarin. The mandarin was the last added a couple months ago.

I don’t think he was skinny. He ate flakes and pellets in the morning and would grab mysis at night. I would also see him picking at the nori clip throughout the day. I haven’t noticed any weird poop from him.

 

[Jay Hemdal Verified Community Expert]

Well, I don’t see any immediately treatable issues, sorry I can’t guess why the blenny died.

Jay