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Call the repairman leave a message, take a lot of pictures then head for your local professional tile supply house. Pick up a grout tool that will remove most grout and buy new grout. The grout will be or should be a powder and mixed with water (in the past you could not mix it with just water because it will crack). Nowadays the powder has an additive that will prevent the grout from cracking. I installed a tile bath in our garage ove 4 years ago and I will say there is not one crack. (and there better not be a crack).