@Pkem did you vaccinate your birds against fowlpox?
Fowlpox is a viral disease in poultry
The infection spreads easily from bird to bird, cage to cage, and through ingestion of standing water in drinkers. Insects can serve as mechanical vectors of poxviruses, spreading infection by depositing virus in the eyes of birds or by biting birds.
The virus can persist in the environment for long hence hygiene should be practiced by regular disinfection of the chicken coup.
Always ensure you vaccinate your birds to prevent such diseases that can slowly reduce your flock's production or even death of the birds. Seek attention from your nearest veterinary doctor to guide on supportive treatment for the sick birds.