I think you’re asking a question about a situation with too many variables for folks here to meaningfully answer. It could be the board, bad cables, amps, speakers…who knows what is distorting?
You need to do some basic troubleshooting outside the live show. Was the distortion sounding like it was on vocals? Plug in a mic and set up your PA and try to recreate the problem.
Without more information, I don’t think anyone here can help without being a psychic.
Good luck!