with Prowin descaler

With a vinegar cleaner.

I have managed to get rid of all the stains in the dishwasher so far.

Appears to be silicone, goes away with vinegar or descaler

I have also cleaned them under water with washing-up liquid and a sponge or dishwashing brush. From time to time I wash them in the dishwasher.

I simply ran the carpet under water with a little washing-up liquid and a sponge on the soft side and the stains went away.