I'm new here!
I'm not new entirely to marine fish keeping. I used to have a marine/reef tank 4 or so years ago but I was a cowboy and it was a bit of a mess! Used tap water from the start, didn't have much money back then etc. I still had limited success with some soft corals and a yellow tang and clownfish surprisingly.
Anyway I've just started again. Cycled a new tank for 3 weeks using some very very cured live rock another reef keeper was selling. It's full of life. I have been testing the water every day for ammonia, nitrite, nitrate, phosphate, calcium, kH, PH and magnesium. I had a small spike a week and a half ago and now ammonia and nitrite are zero and nitrate about 6ppm. Done a waterchange since. Everything else is good.
So I just got two clownfish. They seem fine except one has a white lump on its face. I did not notice this in the shop but it was def there before it got into my tank because I first noticed it when I was floating the bag.
I've taken pictures. Can I upload them here? Anyone any idea how serious this is? Should I return the fish? The other one has no marks or indication of anything wrong. Both are behaving normally.