Poopy butts and roosting?
I'm new to the chicken raising scene, have raised hatch to 8wks old for a breeder, only recently decided to raise some for myself. I won't be much help but I do put 1T ACV to 1 gal of water for drinking (helps digestion, I've read) & doing FF (fermented feeding; firmer poop, less stinky, less poop, no wasted feed & supposedly healthier. There's a thread about it...
Back to your situation, could it be worms? Or probably stress from the move & change, hopefully they're separated/quarantined from your chickens to ensure they don't bring any disease/illness to your flock. You could try a rag/wash towel in warm water, working the poop off their butts and/or trim the poop off then keep the area with warm towel wash.
You could also check in the Raising Backyard Chickens - Emergencies/Disease/Injuries and Cure section for help. I'm sure someone with more expertise will chime in. Hope they get better soon.