First of all I'd get it OUT of the terrarium. I'm not a fan of those personally.
Second, what kind of water do you give it? Tap? Bottled? Distilled? Rain? Tell us!
How much light does it get?

We need more info!

I agree with "tommyr", I would take it out of the terrarium. But its seems that when you removed it from the "cube of death" it went streight into shock. Usually this plastic cubes have the plant sealed in high humidity and despite that you put it in a terrarium, the terrarium humidiyt was still lower then when it was inside those cubes. I also see that because of the stringy stem, it was under very low light conditions.

I see small plantlets growing around the main plants. Be careful not to cut those. To remove the dead leaves, use a small but sharp scissors and gently snipped the dead leaves off. Als, get rid of the grass growing next to it, it will out compete the sundew.

I would suggest that you leave it in the terrarium for know, until it gets used to low levels of humidity. D adelea require high lighting but cool temperatures.

But like "tommyr" said, tell us what soil you are using and what water.

To the left is that species - D. adelae - also a Lowes cube of death plant. I would only snip that which is dead foliage. I would also put it at a window sill.

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