Advice needed on scratching fish treatment options

[Baltimore Bryan]

I need some opinions on what (if anything) I should do for some fish I have. I got all 3 at the same time from the same place, and all looked fine (bangaii cardinal, orchid dottyback, and royal gramma).
The dottyback started scratching on some rocks about a week later, and the gramma began to also a few days after that. The cardinal has never scratched from what I've seen. All fish look fine externally/ no visible white spots or discolored patches of skin or fins. The act normal for the most part, although occasionally the dottyback does kind of hover/ rest on the sand for a minute or two. All are eating fine, water parameters are good, etc.
I treated with PraziPro, thinking it could be flukes, for the recommended dose and repeated 3x as the instructions said. It's been about 2-2.5 weeks since the last dose and the dottyback still scratches (gramma occasionally scratches).
I would have thought that the Prazi would have worked if it were flukes, but I don't see anything else and I can't figure out what it may be. I've also read that sometimes fish continue to scratch after the flukes leave for a time because the tissue that the flukes hooked into remains irritated, so that could be it.
Like I said, they are acting pretty normal, eat well, etc. and I would have expected them to be in worse shape by now if it was a serious infection of some sort. Any thoughts on what could have been the cause, whether I should treat again/ with something else, or just leave them and watch?
Thanks,
Bryan

 

[Newsmyrna80]

How long ago did you acquire them?

 

[Baltimore Bryan]

I got them all about 6 weeks ago.
Bryan

 

[Newsmyrna80]

Ok so you can rule out velvet and Brook. However, ich can not. Back to that in a minute. If the fish did have flukes then yes the scratching could be attributed to the fish's skin healing. So you have some options. You could treat for ich and see if the scratches resolves (I would recommend TT). You could go another round of prazi or just wait it all out and see if the scratching stops. Continue to feed them vitamin enriched food and keep the water very clean.
Are they in a QT or the main?

 

[Baltimore Bryan]

I guess it wouldn't hurt to do more prazi so I can definitely consider that.
It doesn't look like ich and there are no visible white spots on the fins/ fish bodies that I can see, but I know it's such a common disease that it's a possibility. What does "TT" stand for, for the ich treatment you suggested?
They are sort of in "quarantine". They are the only fish in the system, all bought together, and there is no coral or inverts (other than live rock stuff and bristle worms) in the tank. I wanted to make sure they all were doing well before deciding to buy any new fish or inverts for the tank, so they are alone. It does have all of the establish live rock/ sand in it, so I don't want to treat with something that would knock out all of the bacteria and such in there. Otherwise, I am open to some other treatment ideas if needed.
Thanks,
Bryan