I think this will help:
What is wrong with it, or how is it not functioning properly?
If your diffuser is blocked by mineral deposits you could try soaking it in a bag of white vinegar or CLR (calcium, lime, rust-at diy stores and Walmart) taped up so the head is covered in liquid. Or it just maybe worn out and leaking-you'd need to replace it.
Hi She: If you can take it off, place it in a bowl of warm vinegar overnight and in the morning, use a toothpick or straight pin to clean out the holes. Run water through it until it runs free. If you have another problem, and not a mineral blocking the holes problem, please let us know and we will do our best to help. Good luck