Baby unusually silent

My baby boy turned 6 months old today, and has been acting weird since last night. He is usually super hungry after 2 hours of breastfeeding and would cry it out even if I made him wait for just 2 minutes to feed. Last night however it was around 3 hours and he did not complain, was silent and smiling. He drank milk when we provided it though. Now, he woke up at 2am, his usual feed time, but did not show interest in food yet. He continues to stay silent, smiling and drank just a little more than half of what he usually takes. Slept without a noise too. It’s weird because he is usually loud,and cries for food, and makes noises when he sleeps. Any idea what could be going on? Or is he just not hungry?