small pullet not growin and acting strange

[judys hen]

I have a pullet she had an respiratory problem i gave her tylan 50 1/2 cc for three days respiratory cleared up now she seems lethargic and has stopped growing still eats well and drinks but first to roost and last up. gave tylan at 5 -6 month old, now 8 months old.

 

[FlyHigher]

Could it be Cocci or other parasites?