Spot on gill cover of Starlicki Damsel

[trmiv]

I've had this fish in QT for a week now. He's eating well, but he's got this spot on his gill cover that has gotten a little bigger. Not sure what it is. He's in QT with a Tomini tang that doesn't have anything like this on him

Here is a link to some photos of it. Best I could manage
https://drive.google.com/open?id=0Bwh81_NhNfN9aGlrM0RNbF9EWm8