Kitten suddenly not playing/eating little. Safe to wait until tomorrow or emergency vet today?

Last week on Wednesday we found a feral kitten outside. We took it to the vet last Friday and they said kitten was healthy and was around four weeks old. They gave him the first dose of deworming medicine. He was eating wet kitten food and dry kitten food we moistened with water at a good rate. He was very energetic, playing with a wand toy and leaping up on boxes and our bed.

Yesterday I noticed him being less playful and sleeping more. I assumed he was just catching up on sleep after a few days of being up a lot. But last night and this morning he hasn’t eaten a ton. This morning he ate his wet food for a minute or two, and a bit of dry food before cuddling me for a few minutes and then going back to his cat bed. I’m concerned.

His vet is closed today but I’m sure they could get him in tomorrow if I call when they open up. Other vets in my area have a long waitlist for new clients it seems so my only option would be the emergency vet. So you think it is safe to wait until tomorrow or should I do emergency vet today?

I’m an adult in the US. Cat is five weeks old, not neutered.