Worried about my 5 month old

🌻sunrisesunset • Mommy to two beautiful daughters 💓💓| PCOS | 29 | TTC #3
My baby girl is 5 months and usually eats 2 bottles between 11am and 8 pm (12 oz bottles). Yesterday she only ate 1, didn't have a bowel movement and I thought it wasn't a big deal so I gave her 1 oz. of apple juice as our pediatrician reccremended if she wasn't having regular bowel movements and usually within an hour she has one. Well she didn't, and this continued through today. We just gave her another ounce of apple juice and nothing...could she just be getting sick? Or could this be a serious issue? I'm starting to get very worried as she's never slowed on her feeding like this