Diarrhea question

My daughter is 4.5 and she had diarrhea last night for one movement. No fever or anything except right before she said her stomach hurt. She didn’t really eat anything differently except she had an extra serving of blueberries. This has never really happened to us. Does it sound like a bug or just a one time thing? I gave her dry cereal for breakfast. Should I keep up a bland diet or just let her eat like normal (which is actually pretty bland anyway 😂)

Thank you!