anyone else has/had issues during week 6 with getting your baby to stay asleep at night?

she was doing so well before, she developed a pattern and I made a routine around it and it was great! I had a general window for feeding, playing and when she would go down for another sleep. but from the moment we hit week 6 she sleeps well during the day but only takes 30-45 min naps at night until 3am when she finally settles and sleeps at longer intervals for about 1.5 hrs.

absolutely nothing about her routine has changed. she sleeps a lot more during the day now, wakes up to feed and back to sleep. sometimes she would get extra fussy during feedings.