Smokerbill
Free Ranging
Don't commercial egg farms cull out their birds at the time of their 2nd or 3rd molt? That could be what your leghorns were "designed" for, maximum egg production at the expense of a short life.
Did they lay consistently until the end, or did they start having reproductive issues beforehand? I think you mentioned once that if more than one chicken had the same problem you might try to find out the cause of death. When I necropsied my sudden-death hen I found yolks and a soft eggshell where they shouldn't have been, inside the body cavity.
