Breeds that have large or larger combs are very susceptible to frostbite and at 1 degree C, that's close enough to freezing for it to happen with there being moisture from your 7 birds breathing in the coop. Ventilation is key to help dissipate the respiration from the birds. It is the tiny droplets from them breathing that settles on the combs coupled with the cold.
Do put vaseline or Bag Balm on the comb to act as a barrier from the moist.
Also, heat lamps condition the birds to warmth and when it is stopped, either by intention or loss of electricity, the birds are not acclimated to the cold, and problems then occur.
Do put vaseline or Bag Balm on the comb to act as a barrier from the moist.
Also, heat lamps condition the birds to warmth and when it is stopped, either by intention or loss of electricity, the birds are not acclimated to the cold, and problems then occur.