Identify what has failed
Discoloured grout, missing grout, loose tiles and failed silicone are different problems. Photograph the full area and the affected joints. If tiles move, sound hollow or the wall feels damp, say so clearly.
A cosmetic refresh may not solve movement
New grout cannot permanently correct a moving or unsuitable background. The underlying surface, water exposure and extent of any damage need checking before the right repair is agreed.
Keep spare-tile details
If you have matching spare tiles, photograph the box label. If not, include the approximate tile size and a close-up of the colour and finish.