Toddler stomach flu

Yesterday my toddler didn’t eat all day, kept saying she was full and not hungry. Then on a walk around 8, she got really quiet and sleepy. We put her to bed around 9, and then she puked once last night at 9:30, and then all day today she never puked again but has been really lethargic and has had diarrhea most of the day, and is complaining of an ear ache.

Any ideas what’s going on? I know it’s probably a stomach bug, but she only puked once. I have emery phobia so it’s been a rough day. 🙃