If it's like TSC, is it a possibility they got their chicks from Hoover's Hatchery? I've gotten Silkie chicks from TSC, and had issues. Their chicks wasn't healthy.
Maybe you can talk to the store and see if they'll refund? They might want to see the chicks you lost or other means of evidence that you lost them.
On another note, you mentioned the new second hand dog kennel. Maybe you ought to try rulling that out, and try brooding them in something else. Just in case the kennel had a disease on it that wasn't able to be washed off.