Leaf diagnosis
Find the description that matches your plant, then read the cause before acting. Most emergency repotting makes things worse — the majority of these are fixed by changing position or leaving the plant alone.
Stop watering entirely. Move somewhere brighter and warmer so the pot dries. If the stem base is soft, take cuttings now — the parent may not recover.
Soak the pot in a basin for twenty minutes rather than pouring from the top — dry compost repels water. Move away from direct heat.
The plant is reaching for a window. Move it closer to one; almost nothing else will fix this. Cut back the leggy growth once it is in better light.
Normal for a week or two. Do not repot, feed or move it again — let it settle. Water only when the pot feels light.
Rinse the whole plant in the shower, then raise humidity. Check weekly for a month — eggs hatch in waves.
Dab each one with cotton dipped in alcohol. Isolate the plant; they spread to neighbours easily.
Check the least interesting things first: is the pot draining, is there a saucer full of standing water, has a radiator been turned on nearby, has the plant been moved. In our experience four out of five mysteries turn out to be one of those, and the fifth is a pest visible only on the underside of a leaf.