Bummer that your order came in with so many dead.
When I buy meat birds I like to choose a hatchery that is close to my location. Also there are different lineages of CornishX and some do better in the heat and some do better in the cold. You can call around to hatcheries and find out what they offer. I am in the NE and currently raising Ross 308 from
https://www.myerspoultry.com. Next year I want to try something else out of curiosity. And IMO buying all males is worth the upfront cost because they get big faster than the females, better feed conversion.
ROSS 308 AVIAGEN
best 6 week feed conversion
poor feed conversion after 6 weeks
short stocky
cold tolerant
not heat tolerant
often requires early slaughter
ROSS 708
Superior to 308 in all parameters
COBB 500 VANTRESS
slower feed conversion before 6 weeks
best feed conversion after 6 weeks
best overall feed conversion
best uniformity
tall stance
not cold tolerant
heat tolerant
Massive breast
ARBOR ACRES AVIAGEN
medium stance
solid feed conversion until 6 weeks
moderate feed conversion after 6 weeks
higher fat than cobb or ross
MARSHALL
tallest
moderate feed conversion long into 12th week
considerably slower growth than cobb by week 6
lower feed conversion than cobb
higher fat than cobb or ross
more productive and profitable than ARBOR or HUBBARD
HUBBARD CLASSIC
Strong initial growth
good feed conversion
high total yield
good animal welfare
lowest mortality