Kim,
I think one of my fish might have the same problem?...
Seeking advice - shiro utsuri with red spot on fins
I put the fish in a sick tank...I took a scrape of one of the spots, didnt see anything..Not sure if it might be just trauma, I tried anti-bacterial agents for a week...After that didnt work, I tried anti parasite medication that I happened to have, and that didnt really work...I ahve the koi at 75 F and 0.2 to 0.3% salt, still the spots are there, seem to be gettgin a little better perhaps, it has been about 3 weeks.
I think it might be viral. The koi is acting just fine, very active in fact. I have looked and it might be "lymphocystis" and a possible treatment might be acriflavine, but, according to one source it might work...
KoiVet.com - Lymphocystis
but according to the AKCA it is a "flim-flam"...
Koi Diseases
I am by no means an expert, in fact I am still a novice, so take my coments with a grain of salt please. This is probably not helpful for you, but I can at least symphathize with you...I am still wodnering what else I can do for my shiro, if I come up with anything and have any results I will let you know.