Overwatering and root rot

What's happening

Confusingly, a Fittonia drowning in waterlogged soil wilts in almost the same way as a thirsty one. When the roots sit wet they suffocate and begin to rot, so they can no longer pull up water and the leaves go limp — but here a drink makes it worse, not better. Watch for blackening stems and a sour smell at the base.

How to fix it

Stop watering immediately and slip the plant out to check the roots. Trim away any brown, soft, mushy roots with sterilized scissors until only firm, pale tissue remains, then repot into fresh, airy mix in a pot with drainage holes. Let the top of the soil dry slightly before watering again. As insurance, snip a couple of healthy stem cuttings and root them in water — Fittonia roots easily and gives you a backup if the parent doesn't recover.

This is general guidance based on common symptoms; individual plants vary.