Betta Fish: Betta improving but still breathing heavy normal or not?

20g tank, fully cycled:

Ammonia 0

78°

Nitrite 0

Nitrate ~0–5

pH 7.2–7.6

Got a new ~8 month old halfmoon betta 2 days ago. He came in pretty stressed.

Symptoms:

flashing/scratching at first

jittery/erratic swimming (now improved)

eating normally

still resting on bottom/spot in tank sometimes

breathing still kind of heavy, especially after activity

Started API General Cure per label (day 2 dosing).

Swimming is better but breathing hasn’t fully improved yet.. normal recovery or something else?