FlytrapCare Carnivorous Plant Forums

silverfly wrote: ↑Sun May 28, 2023 9:09 pmand it’s been in the same windowsill since I got it.

There's the answer as to why it's declining.
It can be the sunniest windowsill, receiving 23.8 hours of sunlight a day, and the plant will still, slowly die. Modern glass filters sunlight, and what it filters out is what the plant needs for long term health. Outside on a cloudy day is better than a sunny windowsill, that plant needs unfiltered sun.
I'm usually a tough love guy, but your plant is pretty sorry right now, so it will need to be acclimated. Assuming the media is appropriate (just because it's labeled as carnivorous plant media doesn't mean it's right), put it outside in a spot that gets a couple of hours of sun starting at sunrise, no more, and leave it there for a week. The next week put it in a spot that gets three hours, then four hours the next. Eventually leaving it in a spot, outside, with at least six hours of direct sunlight per day.