Had this with two of ours with their first time and our first time lambing. Had to intervene with both as the lambs were in the wrong position and it was quite difficult to correct them. Both had a very light discharge for about a day or two but were fine when turned out in the field. I have noticed this morning one has it again but it just looks a dribble or two, the mum seems fine, eating, walking around, happily feeding lambs so I'll just keep an eye on her. As others have said if it was more than just a bit of bloody discharge then I would call the vet.