OK..lets start at environment. Read about deep litter. Deep litter is beneficial to a coop. If you deep littler you will not have to do all of that spraying and dusting. It will save money and be less work and stress on you.
I recommend you clean out your coop every spring and do your spray and dusting in the coop when all the chicks are out for that day. I white wash the coop the old fashion way once a year.
I understand you are trying to do everything you possibly can do to help your chickens. Sometimes our interventions cause more problems and some people will tell you to medicate, poison, and sterilize the poor critters to death. Too many people have sick and diseased chickens and most of it can be prevented by a healthy normal environment.
I am assuming that your medication for cocci earlier caused your chickens to have a stripped system. It cleaned out every thing. All the good and the bad. Than you compromised it more by adding additional chemicals. This is not your fault. It is what is told to most people. People tell other people if you love your chickens you need to drug them, than drug them more.
In some cases you do need to intervene. Injury is one of them. Land environment with heavy worm loads.
You need to find balance now. Deep litter, ACV.
When you use wormers, antibiotics, chemicals you pretty much are setting the stage for continued problems. You leave the environment sterile and ripe for additional problems. Wormers leave the strong worms behind and just kill off the weak ones who breed stronger worms. Now you have super worms and you need to change wormers to kill them off. The cycle never ends. Feed pumpkins, cucumbers, and probiotocs.
Antibiotics kill off everything and make the survivors strong and mutate. (do you know a family who give antibiotics to their kids for every cold and sniffle? They have the kids at the Dr. office every week and the kids still have runny noses and are never healthy) This is the same thing. Chickens need to build a resistance or be culled.
Put ACV (Brag gs with the mother) in all drinking water. 1 tablespoon for 1/2 gallon.
Give your sick bird some yogurt and scrambled eggs.
Seriously consider feeding your flock fermented feed
