Fantail problem??

I would suggest doing a large water change and run some fresh activated carbon to pull out any remaining medication. Don't use that again (whatever it was) for a while yet. Treating with meds is not a good starting point and this can actually cause other problems you don't want for the fish.

Next, add 1 teaspoon of salt per gallon to the tank.... measure out the amount and predissolve it fully in a bucket of tank water. Add that in slowly wherever the water flow is strongest. Then give this a few days to see if this clears up or if anything new develops.

Before going any further, I'd like to get more specific info.....

What kind of test are you using to check the parameters?
What is your water source and how do you condition it?
How long has the tank been set up? Is it cycled?
How long have you had the fish there?
What would you estimate is the age of your fish?
What do you normally do for tank maintenance and how often?
Also, please list the actual medications you've used and other treatments you've given.. when.. what for.. etc.
Were you running carbon in the filter while you added the ich medicine?
What was the name of the ich medicine you used?
How long was your treatment for ich and what was actually done?

I'd also like to see a photo of that area if you could manage that. It's a lot easier for us to give you better advice when we can actually look and see the appearance ourselves.

Ich does start as a single spot, which will spread into others as the parasite populates. But what we really need to know is if it seems grainy at all. Is the spot smooth? Blotchy? Fuzzy? Do you see anything else that seems different, particularly around the eyes, mouth, gills, belly, or finnage?

If this is not ich, then flex/columnaris is the next likely possibility. That's what the salt treatment is for before proceeding with that any further, as salt helps prevent infection and would keep it from spreading. Pristine water and salt will also clear up a mild case. This also may be viral, so it will help us to find out the answers to the questions I've asked before going any further.

ubermod, this could be one of just a few things, based on your description.
this is definitely not ich, and i wouldn't recommend trying to treat it using ich meds.

one possibility is carp pox, a type of herpes virus that causes large, smooth, waxy growths on the fins and body. these come and go, are usually not contagious and won't harm the fish unless they appear on the gills or in the mouth. they can sometimes be reduced by raising the tank temperature.

another possibility is keratosis, a skin condition that humans get as well. it is simply a thickening of the skin and in fish, it appears as smooth, waxy white bumps on the fins. they most often appear on the edges, near the larger/leading fin rays. this condition is not contagious, is absolutely harmless and the bumps will disappear on their own. it is quite common in goldfish; nothing to worry about. it sometimes results from bottom sitting, sort of like a callus in humans.

i would watch the spot and be sure it does not change color, bubble up or burst. if she eats and acts normally, i wouldn't worry about it. however, as Kashta said, a photo will definitely help us be sure whether it is fungus, virus or keratosis.