Water Leak
One of the tough things about leaks is finding out who the culprit is. It could be the shower, it could be condensate drain line, or abs running up the walls and ceiling! Quoting a client can be incredibly difficult because of this, on top of the problem not being easily identified.
You have to investigate and use common sense at this point; is someone taking too long of a shower? When did the leak start? When did you first notice it? What's the extent of the drywall damage? Can we cut into the drywall to see more?