New Snake Owner Needs HELP!

[i3ora]

I am a new snake owner living in a herp veterinarian deficient area in desperate need of help.
I recently bought a new 1 1/2 year old California Kingsnake from PetSmart who was seemingly healthy at the time I bought him. I received a feeding schedule showing that two weeks before I bought him he had graduated from 3x pinkies to 1x fuzzy every Wednesday. He was usually a very good eater. However, he had not eaten the week before I bought him (probably in preparation of shed). His shed was perfect, no tears and the eyecaps came off nicely. I kept his cage humid. Right now his cage has a gradation, the warm side being 85-90F and the cooler side being 65-70F. The natural lighting of my house is a little darker than what he is used to. Regardless, he is very active and explores his cage and several hides regularly and seems healthy otherwise.

The only issue is that he refuses to eat. He has been on frozen mice his entire life. I even offered the same brand he is used to. Whenever I put him in his feeding container, he shows absolute disinterest in the mouse. The first time I offered a fuzzy (the Wednesday after I bought him), he bit into it, let go and never showed additional interest in any other mice I offered. Every Wednesday I continue offering mice and having to toss them. It has been over a month. I suspect brumation and feel possible weight loss. What should I do?