theres a good photo of birds skin colour on jack barkels post, the best pictures ive seen,,,,,,but i would tend to give them some barley to begin with, and lessen it as the races got further, i maybe wouldnt jump the gun at the respiratory bit, as they are flying an hour, and in this warm weather thats pretty good [ but i would make sure they werent over crowded in the loft] anyway hope all goes well for you