Actually this happened some time ago... I posted a similar question at that time and received little to no response. Water parameters at that time:
I don't have SG
& pH recorded for that time period but they were within normal limits.
Just thought I'd throw this out there again & see what kind of ideas people had. I'll reserach Lympho a bit for my own information.
I'm sure its not an isopod -- there was no LR
or other source for isopods in the tank at that time (unless they can get in some other way?).
I'd welcome any other thoughts on the brown spot. It reminded me of a large pimple -- raised, firm, and appeard to be some swelling under the skin.