The answer to 'tile grimy' is that grimy tiles are typically caused by a buildup of dirt, grime, and soap scum over time. Symptoms include tiles that look discolored, dingy, or stained. The best solutions depend on the severity of the issue.
For light grunge, a thorough cleaning with a tile-safe cleaner and scrub brush may be enough. For tougher grime, you may need to use a grout brush, tile cleaner, and some elbow grease. If the tiles are severely discolored or the grout is cracked, it's best to call a professional tile cleaning service to restore them properly.