Dirty grout

Use a revised brush and grout bite or grout cleaner. Leave on for recommendation time on instructions use the crevis brush to scrub the grout and rinse off. If the mould is in the mastic or sealant (the plastic around the edges making water prove) would properly need replacing). You might away using bleach on this bit but only if you have white tiles and do not leave to sit more than 2 min.

Steam cleaner. If you need any help, get in touch; we can help you. I did a floor recently where we restored the original grout colour

HG do a really good mould remover that you spray and leave on. You can then use a bleach spray to help make it white again.

First of all I would love to know if it's kitchen tiles or bathroom tiles. Simple answer to both. Just mix two parts baking soda with one part of peroxide and dish soap. Spread the paste on the dark grout lines. Leave it for about 15 minutes . Scrub it with your brush and wipe it with warm water. It will come back to the original one for you . Sorry for the late reply. I joined the platform not long ago.

Use a dedicated grout cleaner or a paste of bicarbonate of soda and water. Apply it, leave it for a few minutes, scrub with a stiff grout brush, then rinse well. For mould, use a suitable mould remover and keep the area ventilated. Test any product on a small hidden section first.