Baby exhausted from daycare?

Hi all. My 4 month old son just started daycare. We feel good about his daycare center and he seems to really like it - he smile when he gets there, we get happy photos of him during the day etc. i get him home around 5 and he has been EXHAUSTED the last two nights. Can barely stay awake and is very fussy which he usually never is. I'm hoping it's bc daycare is a lot more stimulation than he's used to so he's just getting used to the change. Has this happened to anyone else? If so did your baby get used to it soon? It's also sad bc we don't get any play time with him before bed bc he's so tired!