Sick juvi. Emperor Angel

[hqgc]

I have a juvi. emperor in my fish only tank. It is from J + L's and it came in with the last Edmonton group order. (aproxx. a month a go).
In the last week I have noticed a white spot or growth on one of his front fins. It is the size equivelent to the tip of a ball point pen. I have to say it looks more like a growth then just a spot.
I have other fish in my tank and all seem fine. Parameters are good , and everybody looks healthy other then the growth.
Any ideas what this could be?