if your hens free range at all they will have some worms. if they are healthy that should not be a problem. i have used pepper flakes before. once a month i give them big pepper flakes for a few days, . they seem to like them.
what kind of mites?some stay on the hens ,others leave and come back.i use wood ash in a big wood box, for them. if it gets out of control. dust them yourself. start there.
leave a big box of wood ash out for them. and dust them every few days yourself.have used a large blow torch in the coop to fry the mites.yes you can have a small fire or too.it will kill any bugs in the coop.
i have had RR,s keep laying for 4 years or more. my current one is 5.5 years old and stopped laying in sept.i like a hen that lays less per week, but more eggs in later years.spring chicks will lay all winter long.