I have 4 chickens. 1 White Rock, 1 Leghorn, 1 Black Sex Linked and 1 Red Sex linked and only the Sex Linked are laying. About 2 months ago my chickens had Foul Pox and while they all recovered, the white rock and leghorn are not laying. They both look perfectly healthy but nothing. Could this be because of the Pox, winter season and less light? Thanks in advanced! Christina.