Baby suddenly sleeping a lot during the day at 2.5 months?

My baby is almost 11 weeks old and he has always been a pretty good sleeper at night. He actually started giving longer stretches at night from around 20 days old.
But for the past 4-5 days, I’ve noticed that he’s been sleeping a LOT during the morning/daytime, especially from around 9:30 AM until 2–3 PM.
He usually wakes up for his bath/massage and feeds, but otherwise he seems very happy to go back to sleep. He does wake up for feeds, but then falls asleep again.

Is this just a developmental/growth-spurt thing, or would you be concerned about a change like this?