Gasping is one of the main signs of aspergillosis. Aspergillosis, a fungal respiratory disease can be treated by an avian vet, but is probably too expensive for most of us. It is also called brooder pneumonia. Sorry about your birds. Here are some good links to read about it:
http://www.thepoultrysite.com/diseaseinfo/7/aspergillosis
http://www.veterinarypartner.com/Content.plx?A=3241&
http://poultrykeeper.com/respiratory-problems/aspergillosis
http://www.multiscope.com/hotspot/aspergillosis.htm
http://www.organicvet.co.uk/Poultryweb/disease/asper/asper1.htm
Quote from Veterinary World:
Aspergillosis/ brooder pneumonia/ mycotic
pneumonia: When the source of the disease is the
hatchery, the disease is called brooder pneumonia.
In older birds, the disease is called aspergillosis. All
birds (domestic poultry, pigeons, canary and zoo bird
species), animals, humans, and plants are
susceptible.
Aspergillosis occurs as an acute disease of
young birds and a chronic disease in mature birds.
Young birds have trouble breathing and gasp for air.
Characteristically, there are no rales or respiratory
sounds associated with aspergillosis. Feed
consumption decreases. Occasionally there is
paralysis or convulsions caused by the fungal toxin.
Mortality in young birds averages 5-20 percent, but
may be as high as 50 percent. Mature birds also
have respiratory distress, reduced feed consumption,
and may have a bluish and dark color of the skin
(cyanosis). Nervous disorders, such as twisted
necks, may occur in a few birds. Mortality in mature
birds is usually less than 5 percent. Aspergillosis is
caused by a fungus. The fungus grows well at room
temperature and higher. All litter and nest materials
(peat moss, peanut hulls, sawdust, peat, bark, straw)
have been known to have been contaminated with
aspergillus. Feed and water should be suspect when
attempting to identify the source of contamination.