Experienced mums - baby vomiting advice plz

On Friday my 6 month old had vaccinations in the morning around 11am. She was super fine, happy and energetic all day. She had dinner about 5pm of some veges and boiled egg (has had egg twice before). Put her down to bed about 6.30 then heard her coughing on the monitor about 7pm. Went in to check on her and her crib was full of vomit and she was white as a ghost and awake but super out of it / floppy.

We rushed her to emergency, all her tests came back fine and they just gave her fluids. She started to get her colour back pretty quickly and after a couple hours of monitoring we were ok to go home.

She was tired the next day but all seemed fine. Doctor couldn’t say for sure what caused it. Could have been a vaccine reaction or some sort of stomach bug. I guess I was leaning towards food as it was closer to eating and had been quite a few hours since the vaccine with no issues. She didn’t show signs of allergic reaction through so maybe more of a bug?

Today is Monday and she’s been fine but has just had another large vomit. She had had some lunch earlier in the day with a few different foods. And seemed fine after vomiting. A little tired and lethargic but colour looked fine.

We’ve just put her down and will monitor her tonight.

My question is, is this all normal / common? I.e for bubs to get upset stomachs, vomiting or react to different bugs that might be about? Or different foods that don’t agree with her? Or does this sound like something more serious? Has anyone had experience with something similar?

We’ll obviously watch for symptoms and if she gets worse will head back to the hospital, but just wondering what might be going on in the meantime.

Sorry for the long post - thanks mommas