Mould on your curtain linings?

If they’re dry clean only, the cleaner will deal with the spores but probably not the stains.

However, what you can try at home is to gather them up and take outside (so the unhealthy spores don’t spread around the room), wipe down with a solution of warm water and Ariel, then rinse with a cloth wrung out in clear vinegar.

The less time the mould has had to form, the easier it’ll be to get rid of the stains.