My 5 month old formula fed daughter has mucus in her poop?

She's been on formula for a couple months now and does great on it. She recently caught a little bit of a cold from me but her doctor said it was just a virus and she would be fine, and she is. She drools A LOT from teething and I read that because of that it could cause some mucus like poop, has anyone else gone through this?? Is it normal or should I take her in to see the doctor??