I don't think you have anything to worry about with your young BRs Cyn, they are very well padded and hardy creatures. I hope your old timers do okay. It's not so much the absolute cold, but the fluctuations between warm and cold that are very hard on animals that are already compromised in some way.
I agree, Mary. Last night was horrible, not for the extreme cold, wasn't that bad, but cold for arthritic birds-- the power went off about midnight. Stayed off for two hours, then back on for 30 minutes, then back off for another two hours. We didn't hook up the solar because the temps were not very cold, still in the upper 30's last night. I remember when Atlas died right before the coldest weather hit us. He was just turning 9 yrs old and I was grateful that his old stiff legs didn't have to go through another hard winter. I woke up with a crashing headache and feeling queasy from the crazy night, better now.
The temps fluctuations didn't help Bash any. I think today or tomorrow may be his last day. He is very unlike himself today. He didn't stand up to eat, to go to his door to stand in the sunshine, not even when I stroked his back. He won't stand at all. He cocks his head to listen, but he has had no food or water today, by choice. He is exactly 9 yrs and 6 mos; I really didn't think he'd live this long, but here he is, no hens and no real life now.
I dug his final resting place at least two years ago so it's ready for him, bless his sweet old heart. He's the sweetest rooster ever, and you know I've had wonderful roosters here, but none that loved to be held and babied like he does. And I did that more and more as he aged. Everyone will miss that boy. Many of my YouTube subscribers adore him, always ask about him. He's had a good life and a long one. Time to rest. Huge hole will be in my barn when he's gone.