I wouldn't rule that out...
he definitely seems "different" as far as personality is concerned.
with his flat affect, i'd say a mood stabilizer.
And It takes a while to regulate the dosage, and to even out... more of his personality will begin to peek through more consistently over time. Hopefully he doesn't revert all the way back, and stays healthy.
And he's just becoming reacquainted with his surroundings after seeing four walls for so long.
again it could take a little while.
but that chick tho...and their interaction is just...