My 6 month old Rhode Island Red named Nellie O. has completely reversed behavior is the past three days. Normally she is number 1 in the pecking order of my flock of 12 hens. Very sassy. Lately she is off by herself with eyes closed. Seems uninterested in anything. No drainage. She is noticeably lighter. She is barely eating or drinking. Tonight I had to physically put her in the coop. I have put antibiotic in their water. Any help would be greatly appreciated.