I know it's normal for them to sometimes go off their food, but my red sided garter seems to have suddenly become frightened of his

I changed him from pinkies to fuzzies and he was taking them well, but suddenly stopped. I tried to introduce the fuzzy gently with the forceps, but he would run away.

I have changed him onto pinkies now. At first, he seems interested and comes across to smell them (tongue going crazy), but he then loses interest and goes off. If I try to introduce it again, he heads for his hide. I know they're stimulated by movement, so I try to make it look like it's alive, but just gently, I don't shake it around. I even tried zombiefying one, but he rejected that one as well.

He ate about a month ago.

His viv is clean and he's in very good health and keeps coming out and inspecting the place and sits looking at us. I handle him occasionally, but not excessively as he doesn't like it as much as the cornsnake.

What should I do? I'm worried that he's gone off mice and I don't know what else to feed him.