Sounds like a loose fitting more than a burst pipe. If the Pipe was burst the interior would be more like a swimming pool
It could be a cracked fitting, the Grey pex is known for that.
Since the water is showing up in the bathroom, I would start with the fittings under the sink, they are the easiest to get to. Second would be the fittings on the rear of the toilet. These sometimes leak after an improper winterizing, or just from age. Last would be the backside of the shower fixture. I am not familiar with your trailer so I cannot offer a "how to" on getting to the back of the shower faucets.