Baby wakes at same time every night

Michelle

For the past month or so, my 13 month old has woken up at the same-ish time every single night. She wakes from like 2am-3am, and I can’t figure out why. Nothing changes in the house at that time, etc. No lights come on, no noises, no changes in temp. Her nap schedules have been weird lately-she’s transitioning to one nap and it’s been an adjustment. Sometimes she naps for 2.5 hours, sometimes 1.5, and sometimes 30mins. 🤷🏻‍♀️ but it never changes her nightly wake up. Other than that, the only change is her bedtime bottle is now whole milk instead of formula. I’ve actually even started using lactose free milk for the past three days to see if it was hurting her tummy, but nothing has changed so far. Any input or experience with this?