I ordered 50 cornish X 3 weeks ago and 8 arrived DOA with 4 more dying that didnt' make it through the night. I called Ideal and told them, they immediately shipped 12 replacements that were very lively. Remember that it is VERY hot in Texas, Tennessee, Arkansas, (pretty much everywhere right now). There were no questions asked, they took my word for the losses, and shipped them immediately. I would say this is excellent customer service. They chicks are monsters right now, I've only lost 3 more. The heat has been unbearable here for the last 2 weeks with no relief in sight.
In hindsight I would not order chicks during this time of year, this was the first time I have ordered chicks in the mail since living in Arkanasas.
Now, did your chicks have a disease? Probably not, IMO, since the symptoms of heat exposure, dehydration, stress are weakness and inability to eat or drink on their own.
Also, my opinion is the handling that they get AFTER the hatchery. Unfortunately this is a whole other discussion regarding the postal service that is very difficult to overcome in the extreme weather conditions that we are experiencing.
Bottom line: Very happy with Ideal Poulty, have ordered several times from them, will order again.