Just today I had one of my chicken buddy come over to bring me a new polish hen. The poor hen was covered in fleas. Then I looked and checked all of my chickens and WOW the same. I have used 7dust and ground sprays all most each week. They wont go away. What can I do? I feel so bad for them. I went and picked a whole jar full out of me sea bright coop but they still come back, Please Help!!!