Rabbit not as energetic

I have a dutch rabbit who's about 10 months old now, and he's not the most energetic rabbit, but today it seems like he's been more sleepy and less excited. When I open the room door, he normally loves to be the first one out and runs downstairs, or when he hears plastic bag crumpling, he usually perks his ears and follows me around the room thinking I have treats. Today, he's not been like that at all. He's been sleeping and he does look like he's comfortable when sleeping. I'm only a little confused because he's eating, drinking and pooping fine. It just seems to be a behavioural problem.

Any reason I should be concerned or worrying, or is this all overthinking?

Follow your gut instinct. If you thing there is something wrong with your rabbit, there probably is. Rabbits are prey animals and hide any symptoms really well. If you are picking up abnormal differences in behaviour, it is probably best to get them checked out at the vet. Rabbits can go downhill very quickly.

Any change in eating habits should ring alarm bells and be treated as an emergency (ie same day vet appointment).

Has he been vaccinated against RHD2 as well as myxo and RHD1? They are 2 separate vaccinations given with a 2 week gap between them. If he hasn't been done, I would discuss it with your vet.

Yes, I agree, go with your gut instincts, you know him best. A vet visit will put your mind at rest. Hope he goes on ok.

I normally get a bunny bouncing towards me in the morning or digging on the door to wake me up. If I don't get that then normally something is wrong. Any change of habits could be something is wrong. I would pop to the vets too, good luck.