4 am wake up with poop

No matter what I do 7 month old always wakes up at 4 am and poops. Have to change of course so won't go back to sleep. I've tried later bed times, extending wake times and baby really only naps 2 hours. I'm so exhausted from constantly waking up at 4. Other child goes to bed around 9 and I go to bed right after that. We have room darkening curtains so it is pitch black. I also have a white noise machine going.

I also can't get her down to 2 or 3 naps. She's still doing 4 30 minute naps no matter what I do. I'm getting frustrated. The baby's sibling doesn't allow her to nap anyway. Always has to be fucking loud if the baby gets to a 45 minute mark.