Lethargic fish! Please help

[BobaFin]

Hello, sorry to bother. I recently purchased two goldfish, a Black Moor and a Oranda. The Oranda seems to be adjusting suprizingly fast to her new tank, but i am a little concerned for my Black Moor. It has been acting more lethargic than my Oranda. At first I thought it was just because it needed some time to adjust (since I got them both yesterday) but this morning I realised he has a small white cloudy area around his left gill. I do have a bottle of treatment for fungus, but im just worried about my fish and would like some advise. It has been sitting at the bottom of the tank for hours until it is feeding time.
Sorry for taking time away from your day!