I am so sorry to hear this. It does sound to me as if some sort of fumes or poison has affected the two birds. Any Teflon pans,air freshners, new carpet, new gas appliance,self clean program on a cooker. All these and more can really affect birds to the extent of death.Have you used new bedding in the cages,try thinking of anything that could be detrimental to the bird. In cases like this it is obvious something has gone very wrong.If neither of the birds have been ill these are the usual causes.Just think of anything new.Sheila