vitamin a deficiency can present with lesion s such as you describe (as well as trichomonisis which will be more yellow in color)... try POLYVISOL Enfamil (this is a childrens liquid A-B-D vitamin) >four drops in beak once a day for a week and in the meantime if it gets worse and more yellow in...
keep your chickens away from the pigeons (especially do not house in the same building):
http://edis.ifas.ufl.edu/UW117
(excerpt)
".... Pigeons have been long associated with disease organisms transmissible to humans and livestock. These include: 13 bacterial diseases including salmonellosis (...