Aw, mama, nakakasad talaga yan na parang nawawala ang spark niya sa school, lalo na't bago pa lang ang transition. Di lang yan aircon issue, kapag may something about the teacher or the environment na off, ramdam talaga ng mga bata yun even if they can't fully explain it, kaya siguro gusto niyang mag-open up pero di pa niya kaya i-articulate properly.
I think okay lang na mag-observe ka muna for a few weeks, pero try din asking her in a softer way, like while you're doing something together (eating, driving, playing) rather than direct questioning, kasi kids open up more naturally na ganyan. If the pattern continues or bumababa ang grades or she gets sick a lot, might be good to chat with her teacher or school counselor para makita nila what's happening sa classroom side, sometimes may social, academic, o personality clash na kailangan i-address by the school. You know your daughter best, mama, so trust that instinct mo.