Maybe ask the local pet store for some supplies to treat your birds cause if your rooster has them then the hens are likely to aswell
Sticktight fleas are common treated by removing them physically with tweezers, and then applying plain Neosporin or Triple Antibiotic Ointment at the sight once a week. Vaseline/petrolatum can also be used to smother the fleas, but they may still need to be removed.
Remove old beeding from coop and burn or physically move it far away. Permethrin spray is safe to use to treat coop and facilities, and lasts for 30 days.
Sevin is carbaryl. Permethrin is different. The main thing is to smother the fleas on the chicken, and remove them. Treating your coop, nests, and roosts are the best way to control them. Unfortunately, that involves changing the bedding, and getting rid of the old. Carbaryl/Sevin dust is no longer approved for poultry. Permethrin or pyrethrins are approved, and are safe to use.