Big white spot appeared on tailpsot blenny

[salajander]

This evening I noticed a large white patch appeared on our tailspot blenny.

It's swimming around normally, active, and doesn't seem to be breathing especially hard.

Two nights ago we added a new Royal Gramma, after a stint in QT.

The other motile tankmates are 3 pajama cardinals, 5 peppermint shrimp, and a handful of hermits and snails.

Any ideas? Is this a disease, or just stress from the new fish?

I'm testing water params now, but they've been steady for a long time.

Full-size images here

 

[salajander]

Maybe just a lesion of some sort? I haven't noticed any signs of aggression between the blenny and the royal gramma, but who knows.