Hi
When I had the same problem I gave my hen natural yoghurt for a few days with a bit of garlic mixed in and its seemed to work but I may have just been lucky!
I also use ACV on a regular basis with all my hens now.
I have 6 bantoms - 2 salmon faverolles, 2 mullberry blues and 2 suffolk chequers although one of the chequers has been poorly of late.
After a trip to the vets and a week on Tylan to clear up an eye infection (which didn't work) and several weeks in and out of the coop in isolation we found the...