Lethargy Remaining in one hidey a lot?

Okay, so I bet this is just me being overprotective, as I lost Oliver a few months ago and I am still pretty sad about it. Greif has me blaming myself which resonates into me being worried about Scout, my next oldest. I bought him a little bin and turned it upside down to use as a hidey, and he loves it – too much? I see him eating and drinking his pellets, hay and veggies and his poops aren't abnormal (he has mighty beautiful poos, if I do say so myself )
But other than eating/drinking/occasional exploring, he's in that hidey. They have the entire area under Harper's 1x2 kitchen which I have lined with a cat bed, a snuggle sack (that Harper uses as a recliner) and a little pillow… Still, in the hidey Scout remains.
He also makes these little whuffly noises that are cute, yes, but could they be a sign of a problem with breathing? He makes them as he wanders around the cage, almost like he's talking to himself.
Should I be worried? Or am I being silly?


Please excuse me, this is my first experience at "motherhood" and I evidently got the worry gene from my Mom, haha.


Edit to add: I've had guinea pigs for a long time in my room and the "whuffly noises" are not like the noises that my other three pigs make. Could it just be his "noise" or should the vet be called?