Those are really just made for damp cupboards and drawers.
Interesting hinged panels around roost, meant to keep heat from lamps contained?
Pics of outside of coop would help....showing any ventilation(from inside too).
Yeah, the sachets are not going to do a thing.
HyGrometers can be used inside and outside the coop to measure the difference, they should pretty much match or you need more ventilation. You can't make the inside of the coop drier than the outside.
Crowding and integration issues can cause...