Don't worry. My chickens eat all the ripe (and partly ripe) nightshade berries around our yard. If chickens can free-range, they know what they can eat, and they know when they can eat it. I only worry about chickens that can't free-range and forage a wide variety of plants, because chickens DO have a desperate need to eat a variety of weeds and greens and they will eat most anything, in desperation. I've known people who penned up their hens and tossed in the same set of weeds for them, day after day. In that case, there's potential for poisoning. You have to work harder & provide a wide variety of weeds, because if they aren't offered, penned chickens can get a toxic overload of something. My hens run around & nibble the following "poisonous" plants around our property: honeysuckle, buttercup, nightshade, laurel berries, cedar fronds, etc... but they also eat little bits of fennel, dead nettles, sunchokes and lots of grass, weeping maple leaves, chickweed, miners lettuce, dandelions, rocket, and kale from the garden (to name just a few I've been able to identify). I've stopped worrying. Supposedly chickens hate the mints and onions? But lo, my hens nibble tiny "medicinal" bits of both these plants, from time to time. They taste everything, even the rhododendrons and the rosemary plants.
I don't know about the electric fence, not having used one. I DO know a friend who installed one after a number of her birds were killed by raccoons and other things. Once they hit the fence, felt the electrical charge, screamed in pain...those creatures never came back. She swears by it, and can leave her chickens in there without worrying for their safety (except from above).
Don't spray your nightshade. I've even eaten the berries (after I saw the chickens gorging themselves) - and I'm still here I think, LOL! It's pretty easy to pull out if you want to remove some. In our neck of the woods probably the only thing I'm nervous about is deadly hemlock. Now that's one thing the chickens will NOT touch. Me neither. I pull it out, tho. I don't spray.