If you were a pint low a I would think about going through your brakes. If you have drums one or both of the cylinders could be leaking. If you have disc then the pads are probably worn. Either way I'd want to know where that fluid went.
Depending on how old the trailer is I'd probably recommend flushing the old brake fluid out and bleeding the brakes at the same time.
Trailers are the most over looked area of boating until your stuck on the side of the road.