Beginner Gardening: What is wrong with my jade plant?, 3 by SianA

SianA wrote:
Hello!
My jade plant used to be strong and have firm, bright green leaves. It looked healthy! Now it's leaves are dull and droopy. Even the stem feels fragile. It has a south facing window with a lot of direct sunlight during the day. I've had it for about a year now. Is it possible it is acting like this because it needs to be repotted? I have maybe been watering a little too much recently... Once, sometimes twice a week although never a lot. How often should it be watered in the winter? It is on the window sill above a radiator but there is a bowl of water on top of the radiator so the air is a little humid.
Also, what is the white fuzz on the plant?
Any help would be greatly appreciated! Thank you,
Sian