How sleepy is too sleepy?

I see this picture posted a lot and it’s really helpful, my baby girl is almost 5 weeks old and yesterday/today she’s been super sleepy whereas the 2-3 days prior she hardly slept.

She’s waking regularly for feeds and is a good weight it’s just that she falls to sleep not too long after a feed and isn’t as interactive as the 2-3 days before but I believe when babies have a development spurt they can be a bit sleepier because this is how the brain develops. I remember from uni something about sleep is the way the body conserves the energy for the brain to form new connections etc.

Has anyone else found their babies sleep patterns to be similar during these periods?