Try a bit of white vinegae + lime juice + dishwashing liquid and dilute it with water.

Then slowly dap a cotton cloth on the mixture and rub it

After that immediately take the sry end of the cloth and rub over the area, them dab the cloth in water a bit and clean it finally and dry it again with dry cotton cloth.

While doing this stretch the area of the pad a bit, will help.

Lemme know if this helps.