Yes molting is hard on them, have you tried ivermectin for the stick tight fleas?Since I have removed one very bad neighbor from the list, my chooks have not been poisoned, taken away, or killed.
Poor little things have enough trouble with molting, not eating right, fleas and egg laying problems.
You will need to do a deep cleaning of the coop though to get rid of them in there, if you are able, remove all the bedding and spray down everything with the pirmethrin, make sure to get into all the cracks and crevices, let it all dry and air out for the day. Then start fresh with new bedding.
But you will need to make sure that the chooks are treated to get rid of them on their body - easiest way is with ivermectin - poor pookies molting and all the other fun things that chickens go through.
I have three here that are 5 yrs old (niece's hens) that have laying issues - Larry lays soft eggs, Sharpie has been laying brittle eggs, they break and make a mess of the other eggs where she lays, and Red of course is not laying eggs at all - I am keeping a close eye on her. Seems the only one of that bunch doing well is Raven.
These older ladies may look robust but I think they are in fact fragile.