First of all, try to remove the mould with a cleaner. We recommend Lithofin KF Mildew-Away* for this application. If residues of mould nevertheless remain or if it has already penetrated the silicone so that it reappears a short time after treatment, you will have to remove the entire joint.
To remove the affected silicone joint, cut it out with a sharp knife or similar. Remove silicone residues without leaving any residues with Lithofin KF Silicone Remover.
Before applying the new joint, treat the area again with Lithofin KF Mildew-Away*.
*Use biocides safely. Always read the label and product information before use.