Hi, hard to tell from the pic, but one of a couple of things could be the culprit... 1. Adhesive hasn't been cleaned out from gaps when wet and grout is too thin in places because of it, creating a shadow behind and darkening up the grout. 2. Tiles are not flat and what you are seeing is shadowing in the bowed section or mismatched edges. 3. Dirty grout or the tiles weren't clean before being grouted and the dust or dirt has been washed into the grout. 4. The cleaning method is at fault. If you use a blue cloth on white grout you will discolour the grout (because it is porous). The first option usually only happens in odd spots so I suspect the cloth used in cleaning has discoloured the grout. This is the culprit most of the time. We usually use ONCE OVER to do the first clean with a light coloured cloth and always use white cloths on white tiles from then on. Cheers

Sprinkle bi carb soda onto grout. Then spray white vinegar onto bi carb powder. This will cause the soda to start bubbling. At that point, rub grout with a toothbrush. Wash over with a damp clean cloth. This is hard work, but worth it. Or, you could get professional tiles cleaners in at a cost.

If you have a spare tile you can take it to Bunnings or your local paint shop and have it paint matched.

A functional backsplash or tiled bathroom can add a wonderful touch to a room with decorative tiling. Although they are attractive and practical, grouting can cause problems. While your tiles may appear shiny and clean, dirt and mildew can easily get stuck between the tiles. These areas should be kept clean and free from mold. (Best Advice From Professional Commercial Cleaning Standards Anyone who wants the brightest, whitest grout for their bathroom is happy to know they don't need to use chemicals. You can easily tackle mildew, dirt, and discoloration with a little elbow grease and constant effort. How To Clean Your Grout And Tiles With Household Ingredients Many household tile cleaners prefer to use simple, diluted forms of bleach or hydrogen peroxide rather than expensive brand-name products. Other household items such as vinegar, baking soda, and lemon juice can also be very helpful. They are ideal for cleaning many situations due to their whitening and antibacterial properties, the natural acids in vinegar, and the abrasive powers of baking soda. However, they can also be used to clean porous joints and remove dirt and stains. These are the two most popular methods, but there are many other tips and tricks that users may have discovered that can save their time. The paste is made up of three parts baking soda and one part water. The paste should be applied to the grouting. After soaking for 10 minutes, rinse off the toothpaste. Another method is to spray the grout with a mixture of lemon juice and bleach in an old spray bottle. After about 20 minutes, rinse off the sprayer. Bleach Or Lemon Juice? There are pros and cons to using chemicals like bleach and acids. A paste or dilute solution of these can be used to quickly clean gaskets and pure white titles. However, these are not the best options. While lemon juice is safe, effective, and versatile, it may not give the same results. These natural grout bleaches can discolor colored grouts, which could negatively affect the appearance of the room. While natural grout and tile cleaning is simple and inexpensive, it does take effort and dedication. It is best to avoid the use of harsh chemicals or steam treatments. Keep up with your cleaning efforts and be sure to use the methods and ingredients mentioned regularly. To prevent stains and spills from building up, clean up immediately. You can also add baking soda paste and lemon juice sprays to your daily bathroom and kitchen cleaning routine. These household grout cleaner Key steps: Regular tile and grout maintenance will slow down the fading process and prevent mold from forming. Cleaning agents that have bleach, like Bleach Spray, can be extremely effective at cleaning lite color tile and grout. It is important to observe the safety instructions on your cleaning product tag or label. A Used toothbrush is a perfect tool for scouring grout. Tiles are much more than just a floor or wall decoration - they can truly be the centerpiece of your kitchen or bathroom. Cleaning the grout is an important part of keeping your tiles looking stunning. While marks rarely appear on black grout, white and gray grout can easily stain and can make a room look dirty even if it's clean. You don't have to consume many hours of scrubbing. Still, there are some great ways to smartly and quickly remove dirt, leaving you time for further satisfying conditioning, If you are wondering how to clean grout and tiles in your kitchen and restroom. What should you use to clean tile and grout? A fundamental element of looking for the most manageable way to cleanse your tile grout. Selecting a tile grout cleaner relies on your choices. if you prefer to use something homemade, options are available. Just make sure you never mix different cleaning solutions, as some combinations (bleach and vinegar, for example) are toxic. Commercial and Domestic Cleaning companies in Melbourne offer specialized grout cleaning solutions that are skilled to restore shine to your grout. When looking at the different options, it's best to choose one that has antifungal properties to help reduce the rate of mold growth, especially in the bathroom where hot and humid environments encourage the spread of the fungus. If you'd rather not use bleach products for tile cleaning, why not try making your own? natural tile cleaner? Grout responds very well to the cleaning powers of acids, such as those found in vinegar, and to the bleaching properties of baking soda. To make an effective tile grout cleaner, simply mix these two products together until they form a thick paste that can be easily applied to the grout.