my frenchie has lost almost 2 lbs in 6 weeks on the exact same food and the vet has done bloodwork twice and cant find anything

Throwing this at the wall because i feel like i am going in circles with our regular vet. Pickle is a 4 year old french bulldog, neutered male, normally a brick at 24 lbs. Six weeks ago at his annual he was 24.1. Last week at a recheck he was 22.4. We have not changed his food (same kibble for almost 2 years), we have not changed his treats, we have not added any new activity. His appetite from the bowl looks identical to me, he still inhales it in 90 seconds.

The vet ran a full chemistry panel and CBC at the first weigh in, all normal. We did fecal, negative. Last week she repeated the bloodwork and added a T4 thyroid, also all in range. She told me to keep monitoring and come back in 6 weeks. I left the appointment feeling like i was being a worried mom about 1.7 pounds but on a 24 lb dog that is almost 8% of his body weight and he definitely looks narrower through the chest in photos compared to december.

Things i have considered. He is fed measured cups twice a day, i havent changed the cup. We did move apartments in march so he has stairs now instead of a one story, so possibly more activity, but he is not a dog who voluntarily moves more, he is a couch potato who barely interrupts a nap for treats. He has not had any GI symptoms, no vomiting, no loose stool, no obvious nausea.

Has anyone been in this spot where the bloodwork was clean and it turned out to be something the standard panels dont catch? Trying to figure out if i push for a referral to internal medicine or if i am being neurotic. The vet was nice but i could tell she thought i was being neurotic.