Does it sound like the start of a stomach bug

Self confessed emetophobe here.. step kid came over Sunday and started vomiting at 1am Monday through to 8am in his room only (put him in quarantine) but was around the other kids Sunday morning when he wasnt displaying signs of sickness. Went back to his Mothers Monday morning at 9am and i went and bleached the entire house. Have kept his room shut since. So its 4 days later and my 6yo has had not diarrhea but kinda tmi mushy poop 3 times in 5 hours. She says she feels fine she just had to poop a lot... now im anxious and worried. Does it sound like the start of something or am i overreacting?

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