Good day, my 3 yr old child often gets white sores in her mouth and her tongue sometimes have a thick white layer. what could be the problem?

Oral Thrush: 31 y/o says, My 3 yr old child gets white sores in her mouth and tongue sometimes have a thick white layer. What could be the problem? Oral Thrush is the name for a common and usually harmless Yeast infection in Babies & Young children who keep much milk in their mouths. Could be from Breast/Bottle feeding or Pacifier. They usually go away without treatment but can see PCP/ Pediatrician for tips