That's thrush. It's caused by Candida albicans. There's nothing wrong with it. My baby got it last week and went to the hospital. The doctor asked me to go to the drugstore to buy a medicine: enzyme tablets, which are made of plastic bottles. Take two tablets, grind them into powder and mix them with cold water. I make utensils with spoons. Dip it in your face and apply it to your mouth three times a day for two or three days. Remember to cook the bottle every day. ! ! !