At 8 months old... have you wormed?
How old is the rest of your flock? Have you had a routine for worming? When, with what? Repeated?
Worms and parasites can cause a variety of symptoms... strangely, even limping and even "respiratory" symptoms, lethargy, death...
Please, pay attention and closely observe every detail and symptom of every chicken in the flock. Also, watch the poop.. follow them around and check the poop... but, remember, just because you don't see worms doesn't mean they don't have them.
If you have never wormed the flock.. or used a wormer that does not kill all worms... use the SEARCH here on BYC to search for "Worming with Valbazen".... it must be given individually, orally, with caution to avoid the windpipe...
You can trust info from dawg53 on worming.... look for more recent years posts. If you have wormed, recently, twice, with Valbazen or Zimecterin Gold, orally and individually... then, there are Antibiotics -- both wormers and antibiotics are available at the local Feed Store... Tetracycline (Duramycin 10) can be added to the water for the whole flock and her individually... 1 tsp. per gallon.. giving only that water with the antibiotic in it, only what they will drink in 24 hours, changing it daily... repeat daily for at least 3 days for the flock (no symptoms) and maybe for 5 to 7 days for her.
If you choose Tylan 50... give it three days in a row... alternating sides... it does damage to the breast tissue to inject anything, but sometimes is necessary. Feed store has syringes, needles and the Tylan 50.
Good luck.. better info, more experience by using the Search here on BYC.
Take care...
