ok now my ribbon snakes won't even eat.

its been over a week, they come out when I present the cut up fish, (I use tilapia fillet, they usually go nuts for it) but they look at it and turn away. and then I have to throw it out after it goes bad,

I know they can brumate when the temperature goes down but the room where they are in is temperature controlled and they have both heating pads and full spectrum uv lighting to self regulate. I'm wondering if they might need to be fed something else. They used to take food every 2 to 3 days in the form of 3 or 4 bite sized chunks of fish.

If brumation is the key, how exactly should I go about that? I think the shed would be way too cold, and I think the basement might be too warm, (I live in eastern Massachusetts near Boston.) I have a smaller 10 gallon tank if that helps, I keep them in a 40 gallon.

everything starts slowing down this time of year regardless of heat they still know the days are getting shorter and winter is coming. start lowering the heat this next month then turn off the heat and lights in Dec. then turn it back on sometime in Jan. should start eating normal in Feb. ish.
No garantee, but that is basically what I do.

Live guppies in a shallow glass bowl might stimulate an eating response.

I have a few snakes that have already stopped eating on their own, usually they come out of it without doing anything but a short brumation usually does the trick if they refuse to eat for a long time. I use a fridge or my basement floor during winter.

Basically you stop feeding with heat on for a week to make sure they digest what's in their system, then turn off heating for a week but keep lights on then lastly turn off the lights and move them somewhere cooler for a month or three or five, depends how North your snakes are from and the reason for brumation. You can brumate them in their tank if that's a doable option or a tub with just a few air holes and moist aspen bedding.