That is good news that your PP is acting better and eating. Remember that Ich goes through life cycle phases. The host fish are still present and unless you do something to interrupt their life cycle of the Ich parasite they will return.
You said that your DT is fallow. Do you intent to keep if fishless for 11-12 weeks?
Your 40G that houses your PP and EA, is it a bare bottomed tank? Are you employing hypo salinity? If so, are you ensuring the salinity in your 40G is maintaned at exactly 1.009? Are you using a properly calibrated refractometer? If you cannot answer yes to all these questions, then the improvment in your PP is likely temporary.
Ich is not going to die naturally. The fish that survive it will build up immunity, and then reinfect your DT and other fish the next time they are stressed.
FWIW, back on 9/21/2014 I had another round of ich in one of my 250G DT's. I was also battling dinoflagellates in that tank, so I decided to nuke that system and start over.
I had a 5" adult Emperor, and adult Blue Ring, Majestic, Passer, Coral Beauty and Eibli angel in that tank, along with a maroon clown, marine betta, a yellow foxface, a rabbitfish, 5 PJ cardinals, a PBT, a Sailfin tang, a harlequin tusk and an adult red coris wrasse. I treated all these fish with a 15 day round of cupramine with absolutely no issues. (Well, I did lose my HT because he jumped out of one of the tanks when I left the safety net off)
All these fish are doing fine and swimming happily in my frag system and my QT's. The cycle on my DT is almost complete, and I plan on slowly reintroducing the fish to the tank this weekend.
We have many of the same fish types. I would guess that your foxface is just being shy in his new home.
Hopefully my experience helps you.
