For these joints i still would go with a non sanded grout.
Repair tile grout shower wall.
If the space is larger than 1 8 of an inch use a sanded grout.
Use a grout saw to remove the loose or damaged grout in between the tiles.
Be careful to avoid damaging the tiles.
Sanded grout is for floors or larger then 1 8 inch tile joints on wall tile.
Links to grout tools.
Match the caulk at most tile specialty shops you can get or order sanded caulk most floor grouts are sanded that will closely match your existing grout color.
Required tools for this grout removal project.
Step 3 clean the seams.
If the width is 1 8 of an inch or smaller use an unsanded grout.
This fix is only practical for interior tile floors and when the gaps between the tiles are 1 4 in.
Measure the space between the tiles.
Then take an old toothbrush and scrub the seams.
Choose the correct type of grout based on the width of your tile joints and where the repair is being done.
Leah demonstrates how to remove damaged grout with a grout saw and then re grout the damaged areas.
Gently run the grout saw back and forth along the grout seams.
You can also purchase an additive to mix with the grout to strengthen its bond to the tile this will help minimize any future cracking.
After the grout has dried for a week protect it with a grout sealer.
Let the grout set up for approximately 20 minutes until a film develops over the tile then clean the area as shown in photos 3 and 4.
Wipe the excess grout and film off the face of the tile with a damp sponge rinsing it often.
Grout is available as sanded or unsanded.
Use a spray bottle and some cold water to wet the areas where you removed the grout.