My 13mo peed the bed, any advice?

My girl has been peeing the bed recently, this is the 2nd time within 3 days she's done it. I take her on 2 walks everyday, once in the morning, and once in the evening. If she doesn't go potty during our evening walks, I'll wait every 30 minutes before taking her again until she goes. With her, it's kinda hard to tell when she needs to potty because she's hardly vocal, so you really need to pay attention for the signs. I just find it a little strange that she all of a sudden started peeing the bed in the middle of the night, please tell me if I'm doing something wrong