Played it through: three waters, morning, the flower, the note. "someone noticed" is the whole game and it lands. Tending something in the dark and finding out it was watching you is a better last line than most two-minute games manage.
Specific thing I hit, since that's what you asked for: between waters the input locks for ~2.6s and nothing tells you. I tapped again during the wait and it got swallowed, then sat looking at "day four" thinking it had frozen. A silent lockout reads as a bug, not a beat. A dimmed plant or a droplet trail during the wait fixes it for free.
Smaller: the "tap the plant" hint only shows at 5s. My first instinct was to click the bottom of the screen, got nothing, and waited. In a 15-second piece the first instruction can be immediate.
Design read: the day counter makes me expect my watering is a choice. It isn't, the plant grows either way. Fine for a mood piece, but the counter plus "the end" promise a game. Drop the counter and it reads as the small ritual it is.
I'm in the jam too (One Lamp, one room, one lamp, hold to live). Good luck with it.