Did you caulk the faucet escutcheons and is the tub spout tight to the wall and caulked? Do you see a water trail? Did you silicone the tub to tile connection instead of grout. Did you silicone where the walls meet instead of grout? If this is a fiberglass tub did you set it in quikcrete or some concrete product? You can take a bucket and splash it on the walls to help identify the location of the leak.