POO questions! Anyone seen anything similar???

We’ve already been to the doctor once last week, and he didn’t seem too worried. And we have her one month appointment on Thursday. She’s nearly 3 months, she isn’t fussier than normal, running a fever or anything like that. But her stools have changed so much and out of the blue, it started a week ago now, no change in my diet (she’s breast fed and 2 bottles a day of Neosure formula), she had had vaccines a week prior to the diarrhea and mucous starting so I don’t feel that’s the cause, she doesn’t seem congested, maybe a little more drooly but nothing major. So, I’m just at a loss, and not sure what the cause could be. Definitely paranoid because she has a pretty good sized umbilical hernia. Have any of you got any advice or opinions on what it could be? My son was always constipated so this is totally new to me 😪