I have a year old speckled sussex who has been incredibly protective from the get-go. However, a few days ago, I noticed he wasn't hanging out with his ladies (they free range). I did introduce 8.5 week old chicks about 2 weeks ago (they all seem perfectly healthy). My rooster will get up and run away from me if I walk towards him and does not seem to have any weakness. However, he will run about 15 feet from me and then he will just stop and seems to fall asleep standing up. His comb is still bright red and I haven't noticed any changes in his poo. All of my other chickens are acting 100% normal. Initially I was concerned about mareks as my young group of chickens is not vaccinated - but my rooster is vaccinated. The timing also doesn't make total sense that he would develop symptoms that quickly..and no one else is acting lethargic. I also did clean out my coop 5 days ago and threw some DE down simply as a preventative (no one has symptoms of mites or lice). Any idea what could be going on?