Our puppy seems a bit sad. Any ideas why?

Our border collie mix puppy is now around 7 months old. She’s always been very hyper and full of energy. She used to take off and do high-speed laps around our living room every night. She was crazy!

In the past few weeks, we’ve noticed she’s calmed down considerably. She almost seems sad. She lies down a whole lot more and she stopped running her laps. I’m a little concerned about it. She was spayed in early April, but the calming down didn’t begin until a month later.

She’s not eating as much as she was, but I assume she’s still teething a bit and we just switched her to adult food per the vet’s suggestion because she was having chronic diarrhea, which has since cleared up. Nothing else has changed.

She’ll still play and do training sessions (with lots of treats) and she’s using the bathroom normally. She’s super happy when my husband and I get home and she still gives us lots of love. She’s very hyper on walks or when we go out, but at home when things are normal, she’s just not as energetic as she once was. It seems too early for her to be calming down.

I found a red bump on her leg two days ago. I took her to the vet who said it looked like an infected insect bite and found two smaller ones on her belly. She gave me antibiotics that we started last night. She didn’t seem too concerned about the puppy’s behavior because she was very energetic at the vet’s office (jumping, barking, etc).

She’s crate trained and is in her crate all night and for a lot of the day because we both work. But this has been the case since she was 8 weeks old, so I don’t see why that would make her sad. And if she’s bored or stir-crazy, I’d think she’d be even more energetic and ready to either run around or tear up our house once she was out for the evening. She’s doing neither.

Should I be concerned or am I just being a worry wart over nothing?