I'm pretty new to backyard chickens (since April), and we have been fighting poultry lice for months now. 3 rounds of poultry dust every 10 days seemed to help one hen, but we've started noticing the other 5 getting the same black markings on their combs as the first one. I've been doing a lot of research: we've fully dusted with permethrin (all 6 hens and hen house) multiple times, I have bathed and redacted each hen, they have been getting monthly ivermectin drops (3-4 between the shoulder blades) once per month for the past two months, and we just recently treated them with fipronil. We also put a kiddie pool in their run containing a mixture of sand, wood ash, and our clay soil for their dust bathing, although the can pretty much dust bathe anywhere in their run (and they definitely do). And they still have lice. Is there something that we're doing wrong, or should we use something else? The 'other pests' that I just found this morning were small, long and slender whitish worms in some chicken poop. I thought that ivermectin was good for both external and internal parasites. Is there something else they should be getting? Thank you for any advice, I really just want our girls to be happy and healthy.