We bought a little guy at Trader Joe’s a few weeks back and about a week ago I managed to feed a stunned fly that I had swatted in the air a little over a week ago. Now the trap with the fly remnants is turning all black like it’s dying. Any thoughts?

There's various reasons why your trap might be turning black. Some will turn black if you overfeed it. Giving it too many insects would be one way. But another way is if the plant is already potted in nutrient-rich soil, it doesn't need the extra nutrients from a prey, and will lose vital energy digesting something it doesn't actually need, and that particular leaf will shut down.

I would not call myself an expert but I've grown them indoors for maybe 15 years. I have five in the terrarium by the window as I write this, in amongst the pitchers and the sundews.

Traps turn black and get replaced all the time. Make sure the plant gets as much direct sun as possible, and keep it soaking in distilled water, and it'll put out more traps to replace that one fairly quickly.

Closest I can do is to say I always enjoyed .... WKRP in Cincinnati

Sorry

Distilled water and do not over feed is the secret.

I don’t use distilled with mine. Just spring water. Always damp or soaking in a mossy mixture. Right now I have 1 trap and 1 pitcher. I rarely feed the trap flies. Just keep it in the kitchen where fruit flies may abound in summer d/t fruit ripening. It’s pretty easy to care for as long as it’s kept damp. You can trim the blackened portions or leave it.
Best of luck! They are fun little plants!